2016 Microchip Technology Inc. DS00002165B-page 1
Highlights
• Single-Chip Ethernet Physical Layer Transceiver
(PHY)
• Comprehensive flexPWR® Technology
- Flexible Power Management Architecture
- LVCMOS Variable I/O voltage range: +1.6V
to +3.6V
- Integ rated 1.2V regulator
• HP Auto-MDIX support
• Miniature 24-pin QFN/SQFN lead-free RoHS
compliant packages (4 x 4mm).
Target Applications
• Set-Top Boxes
• Networked Printers and Servers
• Test Instrumentation
• LAN on Motherboard
• Embedded Telecom Applications
• Video Record/Playback Systems
• Cable Modems/ R ou te rs
• DSL Modems/Routers
• Digital Video Recorders
• IP and Video Phones
• Wireless Access Points
• Digital Televisions
• Digital Media Adapters/Servers
• Gaming Consoles
• POE Applications (Refer to Application Note
17.18)
Key Benefits
• High-Performance 10/100 Ethernet Transceiver
- Compliant with IEEE802.3/802.3u (Fast
Ethernet)
- Compliant with ISO 802-3/IEEE 802.3
(10BASE-T)
- Loop-back modes
- Auto-negotiation
- Automatic polarity detection and correction
- Link status change wake-up detection
- Vendor specific register functions
- Supports the reduced pin count RMII inter -
face
• Power and I/Os
- Various low power modes
- Integrated power-on reset circuit
- Two status LED outputs
- Latch-Up Performance Exceeds 15 0mA per
EIA/JESD 78, Class II
- May be used with a single 3.3V supply
• Additional Features
- Ability to use a low cost 25Mhz crystal for
reduced BOM
• Packaging
- 24-pin QFN/SQFN (4x4 mm) Lead-Free
RoHS Compliant package with RMII
• Environmental
- Extended commercial temperature range
(0°C to +85°C)
- Industrial temperature range version avail-
able (-40°C to +85°C)
LAN8720A/LAN8720AI
Small Footprint RMII 10/100 Ethernet
Transceiver with HP Auto-MDIX Support
TO OUR VALUED CUSTOMERS
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The last character of the literature number is the version number, (e.g., DS30000000A is version A of document DS30000000).
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LAN8720A/LAN8720AI
DS00002165B-page 2 2016 Microchip Technology Inc.
2016 Microchip Technology Inc. DS00002165B-page 3
LAN8720A/LAN8720AI
Table of Content s
1.0 Introduction ..................................................................................................................................................................................... 4
2.0 Pin Description and Configuration .................................................................................................................................................. 6
3.0 Functional Description .................................................................................................................................................................. 14
4.0 Register Descriptions .................................................................................................................................................................... 41
5.0 Operational Characteristics ............................................................................ ............................................................................... 52
6.0 Package Information ..................................................................................................................................................................... 66
7.0 Application Notes .......................................................................................................................................................................... 71
Appendix A: Data Sheet Revision History ........................................................................................................................................... 73
The Microchip Web Site ...................................................................................................................................................................... 74
Customer Change Notification Service ............................................................................................................................................... 74
Customer Support ............................................................................................................................................................................... 74
Product Identification System ............................................................................................................................................................. 75
LAN8720A/LAN8720AI
DS00002165B-page 4 2016 Microchip Technology Inc.
1.0 INTRODUCTION
1.1 General Terms and Conventions
The following is list of the general terms used throughout this document:
BYTE 8-bits
FIFO First In First Out buffer; often used for elasticity buffer
MAC Media Access Controller
RMII™ Reduced Media Independe nt Interface TM
N/A Not Applicable
XIndicates that a logic state is “don’t care” or undefined.
RESERVED Refers to a reserved bit field or address. Unless otherwise
noted, reserved bits must always be zero for write opera-
tions. Unless otherwise noted, values are not guaranteed
when reading reserved bits. Unless otherwise noted, do
not read or write to reserved addresses.
SMI Serial Management Interface
1.2 General Description
The LAN8720A/LAN8720 Ai is a low-power 10BASE-T/100BASE-TX physical layer (PHY) transceiver with variable I/O
voltage that is compliant with the IEEE 802.3-2005 standards.
The LAN8720A/LAN8720Ai supports communication with an Ethernet MAC via a standard RMII interface. It contains a
full-duplex 10-BASE-T/100BASE-TX transceiver and support s 10Mbps (10BASE-T) and 100Mbps (100BASE-TX) oper-
ation. The LAN8720A/LAN8720Ai implements auto-negotiation to automatically determine the best possible speed and
duplex mode of operation. HP Auto-MDIX support allows the use of direct connect or cross-over LAN cables.
The LAN8720A/LAN8720Ai supports both IEEE 802.3-2005 compliant and vendor-specific register functions. However,
no register access is required for operation. The initial configuration may be selected via the configuration pins as
described in Section 3.7, "Configuration Straps," on p age 29. Register-selectable configuration options may be used to
further define the functionality of the transceiver.
Per IEEE 802.3-2005 standards, all digital interface pins are tolerant to 3.6V. The device can be configured to op erate
on a single 3.3V supply utilizin g an inte gr ated 3.3V to 1.2V li nea r regula to r. The linear regulator may be op ti onally dis-
abled, allowing usage of a high efficiency external regulator fo r lower system power dissipation.
The LAN8720A/LAN8720Ai is available in both extended commercial and industrial temperature range versions. A typ-
ical system application is shown in Figure 1-1.
FIGURE 1-1: SYSTEM BLOCK DIAGRAM
LAN8720A/
LAN8720Ai
10/100
Ethernet
MAC
RMII
Mode LED
Transformer
Crystal or
Clock
Oscillator
MDI RJ45
FIGURE 1-2: ARCHITECTURAL OVERVIEW
RMI I Logic
Interrupt
Generator
LEDs
PLL
Receiver
DSP System:
Clock
Data Recovery
Equalizer
Squeltch
& Filters
Analog-to-
Digital
10M RX
Logic
100M RX
Logic
100M PLL
10M PLL
Transmitter
10M
Transmitter
100M
Transmitter
10M TX
Logic
100M TX
Logic
Central Bi as
PHY Address
Latches
LAN8720A/LAN8720Ai
RBIAS
LED1
nINT
XTAL2
XTAL1/CLKIN
LED2
Management
Control
Mode Control
Reset Control
MDIX
Control
HP Auto-MDIX
RXP/RXN
TXP/TXN
TXD[0:1]
TXEN
RXD[0:1]
RXER
CRS_DV
MDC
MDIO
Auto-
Negotiation
RMIISEL
nRST
MODE[0:2]
SMI
PHYAD0
2016 Microchip Technology Inc. DS00002165B-page 5
LAN8720A/LAN8720AI
LAN8720A/LAN8720AI
DS00002165B-page 6 2016 Microchip Technology Inc.
2.0 PIN DESCRIPTION AND CONFIGURATION
FIGURE 2-1: 24-QFN/SQFN PIN ASSIGNMENTS (TOP VIEW)
VSS
NOTE: Exposed pad (VSS) on bottom of package must be connected to ground
LAN8720A/LAN8720Ai
(TOP VIEW)
MDIO
7
8
9
10
11
12
24
23
22
21
20
19
VDD1A
TXN
TXP
RXN
RXP
RBIAS
CRS_DV/MODE2
RXER/PHYAD0
VDDIO
RXD0/MODE0
RXD1/MODE1
Note 2-1 When a lower case “n” is used at the beginning of the signal name, it indicates that the signal is
active low. For example, nRST indicates that the reset signal is active low.
Note 2-2 The buffer type for each signal is indicated in the BUFFER TYPE column. A description of the buffer
types is provided in Section 2.2.
2016 Microchip Technology Inc. DS00002165B-page 7
LAN8720A/LAN8720AI
TABLE 2-1: RMII SIGNALS
Num Pins Name Symbol Buffer
Type Description
1Transmit
Data 0 TXD0 VIS The MAC transmits data to the transceiver using
this signal.
1Transmit
Data 1 TXD1 VIS The MAC transmits data to the transceiver using
this signal.
1Transmit
Enable TXEN VIS
(PD) Indicates that valid transmission da ta is present
on TXD[1:0].
1Receive
Data 0 RXD0 VO8 Bit 0 of the 2 data bits that are sent by the trans-
ceiver on the receive path.
PHY Operat-
ing Mode 0
Configuration
Strap
MODE0 VIS
(PU) Combined with MODE1 and MODE2, this config-
uration strap sets the default PHY mode.
See Note 2-3 for more information on configura-
tion straps.
Note: Refer to Section 3.7.2, "MODE[2:0]:
Mode Configuration," on page 30 for
additional details.
1Receive
Data 1 RXD1 VO8 Bit 1 of the 2 data bits that are sent by the trans-
ceiver on the receive path.
PHY Operat-
ing Mode 1
Configuration
Strap
MODE1 VIS
(PU) Combined with MODE0 and MODE2, this config-
uration strap sets the default PHY mode.
See Note 2-3 for more information on configura-
tion straps.
Note: Refer to Section 3.7.2, "MODE[2:0]:
Mode Configuration," on page 30 for
additional details.
1Receive Error RXER VO8 This signal is asserted to indicate that an error
was detected somewhere in the frame presently
being transferred from the transceiver.
PHY Address
0
Configuration
Strap
PHYAD0 VIS
(PD) This configuration strap sets the transceiver’s SMI
address.
See Note 2-3 for more information on configura-
tion straps.
Note: Refer to Section 3.7.1, "PHYAD[0]: PHY
Address Configuration," on page 26 for
additional information.
LAN8720A/LAN8720AI
DS00002165B-page 8 2016 Microchip Technology Inc.
Note 2-3 Configuration strap values are latched on power-on reset and system reset. Configuration straps are
identified by an underlined symbol name. Signals that function as configuration straps must be
augmented with an external resistor when connected to a load. Refer to Section 3.7, "Configuration
Str ap s, " o n pa ge 29 for additional information.
1Carrier Sense
/ Receive
Data Valid
CRS_DV VO8 This signal is asserted to indi cate the receive
medium is non-idle. When a 10BASE-T packet is
received, CRS_DV is asserted, but RXD[1:0] is
held low until the SFD byte (10101011) is
received.
Note: Per the RMII st andard, transmitted data is
not looped back onto the receive data
pins in 10BASE-T half-duplex mode.
PHY Operat-
ing Mode 2
Configuration
Strap
MODE2 VIS
(PU) Combined with MODE0 and MODE1, this config-
uration strap sets the default PHY mode.
See Note 2-3 for more information on configura-
tion straps.
Note: Refer to Section 3.7.2, "MODE[2:0]:
Mode Configuration," on page 27 for
additional details.
TABLE 2-2: LED PINS
NUM PINS NAME SYMBOL BUFFER
TYPE DESCRIPTION
1
LED 1 LED1 O12 Link activity LED Indication. This pin is driven
active when a valid link is detected and blinks
when activity is detected.
Note: Refer to Section 3.8.1, "LEDs," on
page 32 for additional LED information.
Regulator Off
Configuration
Strap
REGOFF IS
(PD) This configuration strap is used to disable the
internal 1.2V regulator. When the regulator is dis-
abled, external 1.2V must be supplied to VDDCR.
• When REGOFF is pulled high to VDD2A with
an external resistor, the internal regulator is
disabled.
• When REGOFF is floating or pulled low, the
internal regulator is enabled (default).
See Note 2-4 for more information on configura-
tion straps.
Note: Refer to Section 3.7.4, "REGOFF:
Internal +1.2V Regulator Configuration,"
on page 32 for additional details.
TABLE 2-1: RMII SIGNALS (CONTINUED)
Num Pins Name Symbol Buffer
Type Description
2016 Microchip Technology Inc. DS00002165B-page 9
LAN8720A/LAN8720AI
Note 2-4 Configuration strap values are latched on power-on reset and system reset. Configuration straps are
identified by an underlined symbol name. Signals that function as configuration straps must be
augmented with an external resistor when connected to a load. Refer to Section 3.7, "Configuration
Str ap s, " o n pa ge 29 for additional information.
TABLE 2-3: SERIAL MANAGEMENT INTERFACE (SMI) PINS
Num PINs NAME SYMBOL BUFFER
TYPE DESCRIPTION
1SMI Data
Input/Output MDIO VIS/
VOD8 Serial Management Inte rface data input/output
1SMI Clock MDC VIS Serial Management Interface clock
1
LED 2 LED2 O12 Link Speed LED Indication. This pin is driven
active when the operating speed is 100Mbps. It is
inactive when the operating speed is 10Mbps or
during line isolation.
Note: Refer to Section 3.8.1, "LEDs," on
page 32 for additional LED information.
nINT/
REFCLKO
Function
Select
Configuration
Strap
nINTSEL IS
(PU) This configuration strap selects the mode of the
nINT/REFCLKO pin.
• When nINTSEL is floated or pulled to
VDD2A, nINT is selected for operation on the
nINT/REFCLKO pin (default).
• When nINTSEL is pulled low to VSS, REF-
CLKO is selected for operation on the nINT/
REFCLKO pin.
See Note 2-4 for more information on configura-
tion straps.
Note: Refer to See Section 3.8.1.2, "nINTSEL
and LED2 Polarity Selection," on page 33
for additional information.
TABLE 2-4: ETHERNET PINS
Num PINs NAME SYMBOL BUFFER
TYPE DESCRIPTION
1Ethernet TX/
RX Positive
Channel 1
TXP AIO Transmit/Receive Positive Channel 1
1Ethernet TX/
RX Negative
Channel 1
TXN AIO Transmit/Receive Negative Channel 1
TABLE 2-2: LED PINS (CONTINUED)
NUM PINS NAME SYMBOL BUFFER
TYPE DESCRIPTION
LAN8720A/LAN8720AI
DS00002165B-page 10 2016 Microchip Technology Inc.
1Ethernet TX/
RX Positive
Channel 2
RXP AIO Transmit/Receive Positive Channel 2
1Ethernet TX/
RX Negative
Channel 2
RXN AIO Transmit/Receive Negative Channel 2
TABLE 2-5: MISCELLANEOUS PINS
Num PINs NAME SYMBOL BUFFER
TYPE DESCRIPTION
1External
Crystal
Input
XTAL1 ICLK External crystal input
External
Clock Input CLKIN ICLK Single-ended clock oscillator input.
Note: When using a single ended clock
oscillator, XTAL2 should be left
unconnected.
1External
Crystal Out-
put
XTAL2 OCLK External crystal output
1External
Reset nRST VIS
(PU) System reset. This signal is active low.
1Interrupt Out-
put nINT VOD8
(PU) Active low interrupt output. Place an external
resistor pull-up to VDDIO.
Note: Refer to Section 3.6, "Interrupt
Management," on page 24 for additional
details on device interrupts.
Note: Refer to Section 3.8.1.2, "nINTSEL and
LED2 Polarity Selection," on page 32 for
details on how the nINTSEL configuration
strap is used to determine the functio n of
this pin.
Reference
Clock Output REFCLKO VO8 This optional 50MHz clock output is derived from
the 25MHz crystal oscillator. REFCLKO is select-
able via the nINTSEL configuration strap.
Note: Refer Section 3.7.4.2, "REF_CLK Out
Mode," on page 29 for additional details.
Note: Refer to Section 3.8.1.2, "nINTSEL and
LED2 Polarity Selection," on page 32 for
details on how the nINTSEL configuration
strap is used to determine the functio n of
this pin.
TABLE 2-4: ETHERNET PINS (CONTINUED)
Num PINs NAME SYMBOL BUFFER
TYPE DESCRIPTION
TABLE 2-6: ANALOG REFERENCE PINS
Num PINs NAME SYMBOL BUFFER
TYPE DESCRIPTION
1External 1%
Bias Resistor
Input
RBIAS AI This pin requires connection of a 12.1k ohm (1%)
resistor to ground.
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
Note: The nominal voltage is 1.2V and the
resistor will dissipate approximately 1mW
of power.
TABLE 2-7: POWER PINS
Num PINs NAME SYMBOL BUFFER
TYPE DESCRIPTION
1+1.6V to
+3.6V Vari-
able I/O
Power
VDDIO P+1.6V to +3.6V variable I/O power
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
1+1.2V Digita l
Core Power
Supply
VDDCR PSupplied by the on-chip regulator unless config-
ured for regulator off mode via the REGOFF con-
figuration strap.
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
Note: 1 uF and 470 pF decoupling capacitors in
parallel to ground should be used on this
pin.
1+3.3V Chan-
nel 1 Analog
Port Power
VDD1A P+3.3V Analog Port Power to Channel 1
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
1+3.3V Chan-
nel 2 Analog
Port Power
VDD2A P+3.3V Analog Port Power to Channel 2 and the
internal regulator.
Refer to the LAN8720A/LAN8720Ai reference
schematic for connection information.
1Ground VSS PCommon ground. This exposed pad must be con-
nected to the ground plane with a via array.
2016 Microchip Technology Inc. DS00002165B-page 11
LAN8720A/LAN8720AI
2.1 Pin Assignments
TABLE 2-8: 24-QFN PACKA GE PIN ASSIGNMEN TS
Pin NUM Pin Name Pin NUM Pin Name
1VDD2A 13 MDC
2LED2/nINTSEL 14 nINT/REFCLKO
3LED1/REGOFF 15 nRST
4XTAL2 16 TXEN
5XTAL1/CLKIN 17 TXD0
6VDDCR 18 TXD1
7RXD1/MODE1 19 VDD1A
8RXD0/MODE0 20 TXN
9VDDIO 21 TXP
10 RXER/PHYAD0 22 RXN
11 CRS_DV/MODE2 23 RXP
12 MDIO 24 RBIAS
LAN8720A/LAN8720AI
DS00002165B-page 12 2016 Microchip Technology Inc.
2.2 Buffer Types
TABLE 2-9: BUFFER TYPES
BUFFER TYPE DESCRIPTION
IS Schmitt-triggered input
O12 Output with 12mA sink and 12mA source
VIS Variable vol tage Schmitt-triggered input
VO8 Variable voltage output with 8mA sink and 8mA source
VOD8 Variable voltage open-drain output with 8mA sink
PU 50uA (typical) internal pull-up. Unless otherwise noted in the pin description, internal pull-
ups are always enabled.
Note: Internal pull-up resistors prevent unconnected inputs from floating. Do not rely on
internal resistors to drive signals e xternal to the devi ce. When connected to a load
that must be pulled high, an external resistor must be added.
PD 50uA (typical) internal pull-down. Unless otherwise noted in the pin description, internal pull-
downs are always enabled.
Note: Internal pull-down resistors prevent unconnected inputs from floating. Do not rely
on internal resistors to drive signals external to the device. When connected to a
load that must be pulled low, an external resistor must be added.
AI Analog input
AIO Analog bi-directional
ICLK Crystal oscillator input pin
2016 Microchip Technology Inc. DS00002165B-page 13
LAN8720A/LAN8720AI
Note 2-5 The digital signals are not 5V tolerant. Refer to Section 5.1, "Absolute Maximum Ratings*," on
page 54 for additional buffer information.
Note 2-6 Sink and source capabilities are dependent on the VDDIO voltage. Refer to Section 5.1, "Absolute
Maximum Ratings*," on page 54 for additional information.
OCLK Crystal oscillator output pin
PPower pin
TABLE 2-9: BUFFER TYPES (CONTINUED)
BUFFER TYPE DESCRIPTION
LAN8720A/LAN8720AI
DS00002165B-page 14 2016 Microchip Technology Inc.
3.0 FUNCTIONAL DESCRIPTION
This chapter provides functional descriptions of the various device features. These features have been categorized into
the following sections:
•Transceiver
•Auto-negotiation
•HP Auto-MDIX Support
•MAC Interface
•Serial Management Interface (SMI)
•Interrupt Management
•Configuration S traps
•Miscellaneous Functions
•Application Diagrams
3.1 Transceiver
3.1.1 100BASE-TX TRANSMIT
The 100BASE-TX transmit data p ath is shown in Figure 3-1. Each major block is explained in the following subsections.
FIGURE 3-1: 100BASE-TX TRANSMIT DATA PATH
MAC
Tx
Driver
MLT-3
Converter
NRZI
Converter
4B/5B
Encoder
CAT-5RJ45
25MHz by
5 bits
NRZI
MLT-3MLT-3
MLT-3
Scrambler
and PISO
RMII 25MHz
by 4 bits
Ext Ref_CLK
PLL
RMII 50Mhz by 2 bits
MLT-3
Magnetics
125 Mbps Serial
3.1.1.1 100BASE-TX Transmit Data Across the RMII Interface
The MAC controller drives the transmit data onto the TXD bus and asserts TXEN to indicate valid data. The data is
latched by the transceiver’s RMII block on the rising edge of REF_CLK. The data is in the form of 2-bit wide 50MHz data.
3.1.1.2 4B/5B Encoding
The transmit data passes from the RMII block to the 4B/5B encoder. This block encodes the data from 4-bit nibbles to
5-bit symbols (known as “code-groups”) according to Table 3-1. Each 4-bit data-nibble is ma pped to 16 of the 32 pos-
sible code-groups. The remaining 16 code-groups are either used for control information or are not valid.
The first 16 code-groups are referred to by the hexadecimal values of their corresponding data nibbles, 0 through F. The
remaining code-groups are given letter designations with slashes on either side. For example, an IDLE code-group is /
I/, a transmit error code-group is /H/, etc.
2016 Microchip Technology Inc. DS00002165B-page 15
LAN8720A/LAN8720AI
TABLE 3-1: 4B/5B CODE TABLE
CODE
GROUP SYM RECEIVER
INTERPRETATION TRANSMITTER
INTERPRETATION
11110 0 0 0000 DATA 00000 DATA
01001 1 1 0001 — 1 0001 —
10100 2 2 0010 — 2 0010 —
10101 3 3 0011 — 3 0011 —
01010 4 4 0100 — 4 0100 —
01011 5 5 0101 — 5 0101 —
01110 66 0110 — 6 0110 —
01111 77 0111 — 7 0111 —
10010 88 1000 — 8 1000 —
10011 99 1001 — 9 1001 —
10110 AA 1010 — A 1010 —
10111 BB 1011 — B 1011 —
11010 CC 1100 — C 1100 —
11011 DD 1101 — D 1101 —
11100 EE 1110 — E 1110 —
11101 FF 1111 — F 1111 —
11111 IIDLE Sent after /T/R until TXEN
11000 JFirst nibble of SSD, translated to “0101”
following IDLE, else RXER Sent for rising TXEN
10001 KSecond nibble of SSD, translated to
“0101” following J, else RXER Sent for rising TXEN
01101 TFirst nibble of ESD, cause s de -a sse rti o n
of CRS if followed by /R/, else assertion
of RXER
Sent for falling TXEN
00111 RSecond nibble of ESD, causes deasser-
tion of CRS if following /T/, else assertion
of RXER
Sent for falling TXEN
00100 HTransmit Error Symbol Sent for rising TXER
00110 VINVALID, RXER if during RXDV INVALID
11001 VINVALID, RXER if during RXDV INVALID
00000 VINVALID, RXER if during RXDV INVALID
00001 VINVALID, RXER if during RXDV INVALID
00010 VINVALID, RXER if during RXDV INVALID
00011 VINVALID, RXER if during RXDV INVALID
LAN8720A/LAN8720AI
DS00002165B-page 16 2016 Microchip Technology Inc.
3.1.1.3 Scrambling
Repeated data patterns (especially the IDLE code-group) can have power spectral densities with large narrow-band
peaks. Scrambling the da ta helps eliminate these peaks and sp read the signal power more uniformly over the e ntire
channel bandwidth. This uniform spectral density is requir ed by FCC regu lations to prevent excessive EMI from bei ng
radiated by the physical wiring.
The seed for the scrambler is generated from the transceiver address, PHYAD, ensuring that in multiple-transceiver
applications, such as repeaters or switches, each transceiver will have its own scrambler sequence.
The scrambler also performs the Parallel In Serial Out conversion (PISO) of the data.
3.1.1.4 NRZI and MLT-3 Encoding
The scrambler block passes the 5-bit wide parallel data to the NRZI converter where it becomes a serial 125MHz NRZI
data stream. The NRZI is encoded to MLT-3. MLT-3 is a tri-level code where a change in the logic level represents a
code bit “1” and the logic output remaining at the same level represents a code bit “0”.
3.1.1.5 10 0 M Transmit Driver
The MLT3 data is then p assed to the analog transmitter, which drives the differential MLT -3 signal, on outputs TXP and
TXN, to the twisted pair media across a 1:1 ratio isol ation transformer. The 10BASE-T and 100BASE-TX signals pass
through the same transformer so that common “magnetics” can be used for both. The transmitte r drives into the 100
impedance of the CAT-5 cable. Cab le termination and impedance matching require external components.
3.1.1.6 100M Phase Lock Loop (PLL)
The 100M PLL locks onto referen ce clock and generates the 125MHz cl ock used to drive the 125 MHz logic and the
100BASE-TX transmitter.
00101 VINVALID, RXER if during RXDV INVALID
01000 VINVALID, RXER if during RXDV INVALID
01100 VINVALID, RXER if during RXDV INVALID
10000 VINVALID, RXER if during RXDV INVALID
TABLE 3-1: 4B/5B CODE TABLE (CONTINUED)
CODE
GROUP SYM RECEIVER
INTERPRETATION TRANSMITTER
INTERPRETATION
2016 Microchip Technology Inc. DS00002165B-page 17
LAN8720A/LAN8720AI
3.1.2 100BASE-TX RECEIVE
The 100BASE-TX receive data path is shown in Figure 3-2. Each major block is explained in the following subsections.
FIGURE 3-2: 100BASE-TX RECEIVE DATA PATH
MAC
A/D
Converter
MLT-3
Converter
NRZI
Converter
4B/5B
Decoder
Magnetics CAT-5RJ45
PLL
RMII 50Mhz by 2 bits 25MHz by
5 bits
NRZI
MLT-3MLT-3 MLT-3
6 bit Data
Descrambler
and SIPO
125 Mbps Serial
DSP: Timing
recovery, Equalizer
and BLW Correction
MLT-3
RMII 25MHz
by 4 bits
Ext Ref_CLK
3.1.2.1 10 0 M Rece ive In pu t
The MLT-3 from the cable is fed into the transceiver (on inputs RXP and RXN) via a 1:1 ratio transformer. The ADC
samples the incoming differential signal at a rate of 125M samples per second. Using a 64-level quanitizer , it generates
6 digital bits to represent each sample. The DSP adjusts the gain of the ADC according to the observed signal levels
such that the full dynamic range of the ADC ca n be used.
3.1.2.2 Equalizer, Baseline Wander Correction and Clock and Data Recovery
The 6 bits from the ADC are fed into the DSP block. The equalizer in the DSP section compensates for phase and ampli-
tude distortion cause d by the physical channel consisting of magneti cs, connectors, and CAT- 5 cable. The e qualizer
can restore the signal for any good-quality CAT-5 cable between 1m and 150m.
If the DC content of the signal is such that the low-frequency components fall below the low frequency pole of the iso-
lation transformer , then the droop characteristics of the transformer will become significant and Baseline W ander (BLW)
on the received signal will result. To prevent corruption of the received data, the transceiver corrects for BLW and can
receive the ANSI X3.263-1995 FDDI TP-PMD defined “killer packet” with no bit errors.
The 100M PLL generates multiple phases of the 125MHz clock. A multiplexer, controlled by the timing unit of the DSP,
selects the optimum phase for sampling the data. This is used as the received recovered clock. This clock is used to
extract the serial data from the received signal.
3.1.2.3 NRZI and MLT-3 Decoding
The DSP generates the MLT-3 recovered levels that are fed to the MLT-3 converter. The MLT-3 is then converted to an
NRZI data stream.
3.1.2.4 Descrambling
The descrambler performs an inverse function to the scrambler in the transmitter and also performs the Serial In Parallel
Out (SIPO) conversion of the data.
During reception of IDLE (/I/) symbols. the descrambler synchronizes its descrambler key to the incoming stream. Once
synchronization is achieved, the descrambler locks on this key and is able to descramble incoming data.
LAN8720A/LAN8720AI
DS00002165B-page 18 2016 Microchip Technology Inc.
Special logic in the descramb ler ensures synchronization with the remote tran sceiver by searching for IDLE symbols
within a window of 4000 bytes (40us). This window ensures that a maximum packet size of 1514 bytes, allowed by the
IEEE 802.3 standard, can be received with no interference. If no IDLE-symbols are detected within this time-period,
receive operation is aborted and the descrambler re-starts the synchronization process.
3.1.2.5 Alignment
The de-scrambled signal is then aligned into 5-bit code-groups by recognizing the /J/K/ S tart-of-Stream Delimiter (SSD)
pair at the start of a packet. Once the code-word alignment is determined, it is stored and utilized until the ne xt start of
frame.
3.1.2.6 5B/4B Decoding
The 5-bit code-groups are translated into 4-bit data nibbles according to the 4B/5B table. The translated data is pre-
sented on the RXD[1:0] signal lines. The SSD, /J/K/, is translated to “0101 0101” as the first 2 nibbles of the MAC pre-
amble. Reception of the SSD causes the transceiver to assert the receive data valid signal, indicating that valid data is
available on the RXD bus. Successive valid code-groups are translated to data nibbles. Reception of either the End of
Stream Delimiter (ESD) consisting of the /T/R/ symbols, or at least two /I/ symbols causes the transceiver to de-assert
the carrier sense and receive data valid signals.
Note: These symbols are not translated into data.
3.1.2.7 Receive Data Valid Signal
The Receive Data Valid signal (RXDV) indicates that recovered and decoded nibbles are being presented on the
RXD[1:0] outputs synchronous to RXCLK. RXDV becomes active after the /J/K/ delimiter has been recognized and RXD
is aligned to nibble boundaries. It remains active until either the /T/R/ delimiter is recognized or link test indicates failure
or SIGDET becomes false.
RXDV is asserted when the first nibble of translated /J/K/ is ready for transfer over the Media Independent Interface (MII
mode).
FIGURE 3-3:
5D5 data data data data
RXD
RX_DV
RX_CLK
5D5data data data data
CLEAR-TEXT 5JK
555
TR
Idle
RELATIONSHIP BETWEEN RECEIVED DATA AND SPECIFIC MII SIGN ALS
3.1.2.8 Receiver Errors
During a frame, unexpected code-groups are considered receive errors. Expected code groups are the DATA set (0
through F), and the /T/R/ (ESD) symbol pair. When a receive error occurs, the RXER signal is asserted and arbitrary
data is driven onto the RXD[1:0] lines. Should an error be detected during the time that the /J/K/ delimiter is being
decoded (bad SSD error), RXER is asserted true and the value ‘1110’ is driven onto the RXD[1:0] lines. Note that the
Valid Data signal is not yet asserted when the bad SSD error occurs.
3.1.2.9 100 M Re ce ive Da ta Across the RMII In te rfa ce
The 2-bit data nibbles are sent to the RMII block. These data nibbles are clocked to the controller at a ra te o f 50MH z.
The controller samples the data on the rising edge of XTAL1/CLKIN (REF_CLK). To ensure that the setup and hold
requirements are met, the nibbles are clocked ou t of the transceiver on the falling edge of XTAL1/CLKIN (REF_CLK).
3.1.3 10BASE-T TRANSMIT
Data to be transmitted comes from the MAC layer controller. The 10BASE-T transmitter receives 4-bit nibbles from the
MII at a rate of 2.5MHz and converts them to a 10Mbps serial data stream. The data stream is then Manchester-encoded
and sent to the analog transmitter, which drives a signal onto the twisted pair via the external magnetics.
The 10M transmitter uses the fol lowing blocks:
2016 Microchip Technology Inc. DS00002165B-page 19
LAN8720A/LAN8720AI
• MII (digital)
• TX 10M (digital)
• 10M Transmitter (analog)
• 10M PLL (analog)
3.1.3.1 10M Transmit Dat a Across the RMII Interface
The MAC controller drives the tran smi t data onto th e TX D bu s. T XD[1 :0] shall tra nsition syn chrono usly wi th respect to
REF_CLK. When TXEN is a sserted, TXD[1:0] are acce pted for transmission by the d evice. TXD[1:0] shall be “00” to
indicate idle when TXEN is deasserted. Values of TXD[1:0] other than “00” when TXEN is deasserted are reserved for
out-of-band signaling (to be defined). V alues other than “00” on TXD[1:0] while TXEN is deasserted shall be ignored by
the device.TXD[1:0] shall provide valid data for each REF_CLK period while TXEN is asserted.
In order to comply with legacy 10BASE-T MAC/Controllers, in half-duplex mode the transceiver loops back the trans-
mitted data, on the receive path. This does not confuse the MAC/Controller since the COL signal is not asserted during
this time. The transceiver also supports the SQE (Heartbeat) sig nal.
3.1.3.2 Manchester Encoding
The 4-bit wide data is sent to the 1 0M TX block. The nibble s are conve rted to a 10Mb ps serial NRZI data stream. The
10M PLL locks onto the external clock or internal oscillator and produces a 20MHz clock. This is used to Manchester
encode the NRZ data stream. When no data is being transmitted (TXEN is low), the 10M TX block outputs Normal Link
Pulses (NLPs) to maintain communications with the remote link partner.
3.1.3.3 10M Transmit Drivers
The Manchester encoded d ata is sent to th e analo g tran sm itter w here it is shape d a nd fi ltered before bei ng driven out
as a differential signal across the TXP and TXN outputs.
3.1.4 10BASE-T RECEIVE
The 10BASE-T receiver gets the Manchester- encoded analog signal from the cable via the magnetics. It recovers the
receive clock from the signal and uses this clock to recover the NRZI data stream. This 10M serial data is converted to
4-bit data nibbles which are passed to the controlle r via MII at a rate of 2.5MHz.
This 10M receiver uses the followi ng blocks:
• Filter and SQUELCH (analog)
• 10M PLL (analog)
• RX 10M (digital)
• MII (digital)
3.1.4.1 10M Receive Input and Squelch
The Manchester signal from the cable is fed into the transceiver (on inputs RXP and RXN) via 1:1 ratio magnetics. It is
first filtered to reduce any out-of-band noise. It then passes through a SQUELCH circuit. The SQUELCH is a set of
amplitude and timing comparators that normally reject differential voltage levels below 300mV and detect and recognize
differential voltages above 585mV.
3.1.4.2 Manchester Decoding
The output of the SQUELCH goes to the 10M RX block where it is validated as Manchester encoded data. The polarity
of the signal is also ch ecked. If the polarity is reversed (local RXP is connected to RXN of the remote partner and vice
versa), the condition is identified and corrected. The reversed condition is indicated by the XPOL bit of the S pecial Con-
trol/Status Indications Register. The 10M PLL is locked onto the received Manchester signal, from which the 20MHz
cock is generated. Using this clock, the Manchester encode d data is extracted and converted to a 10MHz NRZI data
stream. It is then converted from serial to 4-bit wide parallel data.
The 10M RX block also detects valid 10Base-T IDLE signals - Normal Link Pulses (NLPs) - to maintain the link.
3.1.4.3 10M Receive Data Across the RMII Interface
The 2-bit data nibbles are sent to the RMII block. These data nibbles are valid on the rising edge of the RMII REF_CLK.
LAN8720A/LAN8720AI
DS00002165B-page 20 2016 Microchip Technology Inc.
3.1.4.4 Jabber Detection
Jabber is a condition in which a station transmits for a period of time longer than the maximum permissible packet length,
usually due to a fault condition, which results in holding the TXEN input for a long period. S pecial logic is used to detect
the jabber state and abort the transmission to the line within 45ms. Once TXEN is deasserted, the logic resets the jabber
condition.
As shown in Section 4.2.2, "Basic Status Register," on page 45, the Ja bber Detect bit indicates tha t a jabbe r conditi on
was detected.
3.2 Auto-negotiation
The purpose of the auto-negotiation function is to automatically configure the transceiver to the optimum link parameters
based on the capabilities of its link partner. Auto-negotiation is a mechanism for exchan ging configuration informa tion
between two link-partners and automatically selecti ng the highest performance mode of operation supported by both
sides. Auto-negotiation is fully defined in clause 28 of the IEEE 802.3 specification.
Once auto-negotiation has co mpleted, information about th e resolved link can be passed back to the controller via the
Serial Management Interface (SMI). The results of the negotiation proc ess are re flecte d in the Speed Indication bits of
the PHY S pecial Control/S tatus Register, as well as in the Auto Negotiation Link Partner Ability Register. The auto-nego-
tiation protocol is a purely physical layer activity and proceeds independently of the MAC controller.
The advertised capabilities o f the transceiver are stored in the Auto Negotiation Advertisement Register. The default
advertised by the transceiver is determined by user-defined on-chip signal options.
The following blocks are activated during an Auto-negotiation session:
• Auto-negotiation (digital)
• 100M ADC (analog)
• 100M PLL (analog)
• 100M equalizer/BLW/clock recovery (DSP)
• 10M SQUELCH (analog)
• 10M PLL (analog)
• 10M Transmitter (analog)
When enabled, auto-negotiation is started by the occurrence of one of the following events:
• Hardware reset
• Software reset
• Power-down reset
• Link status down
• Setting the Restart Auto-Negotiate bit of the Basic Control Register
On detection of one of these events, the transceiver begins auto-negotiation by transmitting bursts of Fast Link Pulses
(FLP), which are bursts of link pulses from the 10M transmitter. They are shaped as Normal Link Pulses and can pass
uncorrupted down CAT-3 or CAT-5 cable. A Fast Link Pulse Burst consists of up to 33 pu lses. The 17 odd-numbered
pulses, which are always present, frame the FLP burst. The 16 even-numbered pulses, which may be present or absent,
contain the data word being transmitted. Presence of a data pulse represents a “1”, while absence represents a “0”.
The data transmitted by an FLP burst is known as a “Link Code W ord.” These are defined fully in IEEE 802.3 clause 28.
In summary, the transce iver advertises 802.3 co mpliance in its selector fi eld (the first 5 bits of the Link Code Word). It
advertises its technology ability according to the bits set in the Auto Negotiatio n Advertisement Register.
There are 4 possible matches of the technology abilities. In the order of priority these are:
• 100M Full Duplex (Highest Priority)
• 100M Half Duplex
• 10M Full Duplex
• 10M Half Duplex (Lowest Priority)
If the full capabilities of the transceiver are advertised (100M, Full Duplex), and if the link partner is capable of 10M and
100M, then auto-negotiation selects 100M as the highest performance mode. If the link partner is capable of half and
full duplex modes, then auto-negotiation selects full duplex as the highest performance operation.
2016 Microchip Technology Inc. DS00002165B-page 21
LAN8720A/LAN8720AI
Once a capability match has been determined, the link code words are repeated with the acknowledge bit set. Any dif-
ference in the main con tent of the link code words at this time will cause auto-negotiation to re-start. Auto-negotiation
will also re-start if not all of the required FLP bursts are received.
The capabilities advertised during auto-negotiation by the transceiver are initially determined by the logic levels latched
on the MODE[2:0] configuration straps after reset completes. These configuration straps can also be used to disable
auto-negotiation on power-up. Refer to Section 3.7.2, "MODE[2:0]: Mode Configuration," on page 30 for additional infor-
mation.
Writing the bits 8 through 5 of the Auto Negotiation Advertisement Regi ster allows software control of the capabilities
advertised by the transceiver . Writing the Auto Negotiation Advertisement Register does not automatically re-start auto-
negotiation. The Restart Auto-Negotiate bit of the Basic C ontrol Register must be set before the new abilities will be
advertised. Auto-negotiation can also be disabled via software by clearing the Auto-Negotiation Enable bit of the Basic
Control Register.
Note: The device does not support “Next Page” capability.
3.2.1 PARALLEL DET ECT IO N
If the LAN8720A/LAN8720 Ai is connected to a device lacking the ability to auto-negotiate (for example, no FLPs are
detected), it is able to determine the speed of the link based on either 100M ML T -3 symbols or 10M Normal Link Pulses.
In this case the link is presumed to be half duplex per the IEEE standard. This ability is known as “Parallel Detection.”
This feature ensures interoperability with legacy link partners. If a link is formed via parallel detection, then the Link Part-
ner Auto-Negotiation Able bit of the Auto Negotiation Expansion Register is cleared to indicate that the Li nk Partner is
not capable of auto-negotiation. The control ler has access to this information via the management interface. If a fault
occurs during parallel detection, the Parallel Detection Fault bit of Link Partner Au to-Negotiation Able is set.
Auto Negotiation Link Partner Ab ility R egister is use d to sto re the lin k partner ability i nformation, w hich is coded in the
received FLPs. If the link partner is not auto-negotiation capable, then the Auto Negotiation Link Partner Ability Register
is updated after completion of parallel detection to reflect the speed capability of the link partner.
3.2.2 RESTARTING AUTO-NEGOTIATION
Auto-negotiation can be restarted at any time by se tting the Restart Auto-Negotiate bit of the Basic Control Register.
Auto-negotiation will also restart if the link is broken at any time. A broken link is caused by signal loss. This may occur
because of a cable break, or because of an interruption in the signal tra nsmitted by the link partner. Auto-negotiation
resumes in an attempt to determine the new link configuration.
If the management entity re-starts auto-negotiation by se tting the Restart Auto-Negotiate bit of the Basic Control Reg-
ister, the LAN8720A/LAN8720Ai will resp ond b y stop ping all tr an smi ssion/receivi ng operation s. Once the b reak_link_ -
timer is completed in the Auto -n egoti ati on state-machine ( approximately 120 0ms), auto-ne gotiation will re-start. In this
case, the link partner will have also dropped the link d ue to l ack of a received sign al, so it too wil l resu me auto-ne goti -
ation.
3.2.3 DISABLING AUTO-NEGOTIATION
Auto-negotiation can be disable d by setting the Auto-Negotiation Enable bit of the Basic Control Register to zero. The
device will then force its speed of operation to reflect the information in the Basic Control Register (Sp eed Select bit and
Duplex Mode bit). These bits should be ignored when auto-negotiation is enabled.
3.2.4 HALF VS. FULL DUPLEX
Half duplex operation relies on the CSMA/CD (Carrier Sense Multiple Access / Collision Detect) protocol to handle net-
work traffic and collisions. In this mode, the carrier sense signal, CRS, responds to both transmit and receive activity. If
data is received while the transceiver is transmitting, a collision results.
In full duplex mo de, the transceiver is able to transmit and re ceive data simultaneously. In this mode, CRS respo nds
only to receive activity. The CSMA/CD protocol doe s not apply and collision detection is disabled.
3.3 HP Auto-MDIX Support
HP Auto-MDIX facilitates the use of CAT-3 (10BASE-T) or C AT- 5 (100BASE-T) medi a UTP inte rco nnect cab le without
consideration of interface wiring scheme. If a user plugs in either a direct connect LAN cable, or a cross-over patch
cable, as shown in Figure 3-4, the device’s Auto-MDIX transceiver is capable of configuring the TXP/TXN and RXP/RXN
pins for correct transceiver operation.
LAN8720A/LAN8720AI
DS00002165B-page 22 2016 Microchip Technology Inc.
The internal logic o f the device detects the TX and RX pins of the connecting device. Since th e RX and TX line pairs
are interchangeable, special PCB design considerations are needed to a ccommodate the symmetrical magnetics a nd
termination of an Auto-MDIX design.
The Auto-MDIX function can be disabled via the AMDIXCTRL bit in the Special Control/Status Indications Register.
FIGURE 3-4: DIRECT CABLE CONNECTION VS. CROSS-OVER CABLE CONNECTION
1
2
3
4
5
6
7
8
TXP
TXN
RXP
Not Used
Not Used
RXN
Not Used
Not Used
1
2
3
4
5
6
7
8
TXP
TXN
RXP
Not Used
Not Used
RXN
Not Used
Not Used
Direct Connect Cable
RJ-45 8-pin straight-through
for 10BASE-T/100BASE-TX
signaling
1
2
3
4
5
6
7
8
TXP
TXN
RXP
Not Used
Not Used
RXN
Not Used
Not Used
1
2
3
4
5
6
7
8
TXP
TXN
RXP
Not Used
Not Used
RXN
Not Used
Not Used
Cross-O ver Cable
RJ-45 8-pin cross-over for
10BASE-T/100BASE-TX
signaling
3.4 MAC Interface
3.4.1 RMII
The device supports the low pin count Reduced Media Independent Interface (RMII) intended for use between Ethernet
transceivers and switch ASICs. Under IEEE 802.3, an MII comprised of 16 pins for data and control is defined. In devices
incorporati ng many MACs or transceiver in terfaces such as switches, the number of pins can add significant cost as the
port counts increase. RMII reduces this pin count while retaining a management interface (MDIO/MDC) that is identical
to MII.
The RMII interface has the following characteristics:
• It is capable of supporting 10Mbps and 100Mbps data rates
• A single clock reference is used for both transmit and receive
• It provides independent 2-bit (di-bit) wide transmit and receive data paths
• It uses LVCMOS signal levels, compatible with common digital CMOS ASIC processes
The RMII includes the following interface signals (1 optional):
• transmit data - TXD[1:0]
• transmit strobe - TXEN
• receive data - RXD[1:0]
• receive error - RXER (Optional)
• carrier sense - CRS_DV
• Reference Clock - (RMII references usually define this signal as REF_CLK)
2016 Microchip Technology Inc. DS00002165B-page 23
LAN8720A/LAN8720AI
3.4.1.1 CRS_DV - Carrier Sense/Receive Data Valid
The CRS_DV is asserted by the device when the receive medium is non-idle. CRS_DV is asserted asynchronously on
detection of carrier due to th e criteria releva nt to the operating mode . In 10BASE-T mode when squel ch is passed, or
in 100BASE-X mode when 2 non-contiguous zeros in 10 bits are detected, the carrier is said to be detected.
Loss of carrier shall result in the deassertion of CRS_DV synchronous to the cycle of REF_CLK which presents the first
di-bit of a nibble onto RXD[1:0] (for example, CRS_DV is deasserted only on nibble boundaries). If the device has addi-
tional bits to be presented on RXD[1:0] following the initial deassertion of CRS_DV, then the device shall assert
CRS_DV on cycles of REF_CLK which present the second di-bit of each nibble and de-assert CRS_DV on cycles of
REF_CLK which present the first di-bit of a nibble. The result is, starting on nibble boundaries, CRS_DV toggle s at 25
MHz in 100Mbps mode and 2.5 MHz in 10Mbps mode when CRS ends before RXDV (for example, the FIFO still has
bits to transfer when the carrier event ends). Therefore, the MAC can accurately recover RXDV and CRS.
During a false carrier event, CRS_DV shall remain asserted for the duration of carrier activity. The data on RXD[1:0] is
considered valid once CRS_DV is asserted. However, since the assertion of CRS_DV is asynchronous relative to
REF_CLK, th e d ata on RXD[1:0] sha ll be “00 ” until proper receive signal decoding takes place.
3.4.1.2 Reference Clock (REF_CLK)
The RMII REF_CLK is a continuous clock that provides the timing reference for CRS_ DV, RXD[1:0], TXEN, TXD[1:0]
and RXER. The device uses REF_CLK as the network clock such that no buffering is required on the transmit data path.
However , on the receive data path, the receiver recovers the clock from the incoming data stream, and the device uses
elasticity buffering to accommodate for differences between the recovered clock and the local REF_CLK.
3.5 Serial Management Interface (SMI)
The Serial Management Interface is used to control the device and obtain its st atus. This interface supports registers 0
through 6 as required by Clause 22 of the 802.3 standard, as well as “vendor-specific” registers 16 to 31 allowed by the
specification. Non-supported registers (such as 7 to 15) will be read as hexadecimal “FFFF”. Device registers are
detailed in Section 4.0, "Register Descriptions," on page 43.
At the system level, SMI provides 2 signals: MDIO and MDC. The MDC signal is an aperiodic clock provided by the
station management controller (SMC). MDIO is a bi-directional data SMI input/output signal that receives serial data
(commands) from the controller SMC and sends serial data (status) to the SMC. The minimum time b etween edges of
the MDC is 160 ns. There is no maximum time between edges. The minimum cycle time (time between two consecutive
rising or two consecutive fallin g edges) is 400 ns. These modest timi ng requirements allow this interface to be easily
driven by the I/O port of a microcontroller.
The data on the MDIO line is latched on the rising edge of the MDC. The frame structure and timing of the data is shown
in Figure 3-5 and Figure 3-6. The timing relationships of the MDIO signals are further d escribed in Sectio n 5.5.6, "SMI
Timing," on page 64.
FIGURE 3-5:
MDC
MDIO
Read Cycle
...
32 1's 0110A4A3A2A1A0R4R3R2R1R0 D1
...
D15 D14 D0
Preamble Start of
Frame OP
Code PHY Address Register Address Turn
Around Data
Data From Phy
Data To Phy
MDIO TIMING AND FRAME STRUCTURE - READ CYCLE
LAN8720A/LAN8720AI
DS00002165B-page 24 2016 Microchip Technology Inc.
FIGURE 3-6:
MDC
MDIO ...
32 1's 0 1 10 A4A3A2A1A0R4R3R2R1R0
Write Cycle
D15 D14 D1 D0
...
DataPreamble Start of
Frame OP
Code PHY Address Register Address Turn
Around
Data To Phy
MDIO TIMING AND FRAME STRUCTURE - WRITE CYCLE
3.6 Interrupt Management
The device management interface supports an interrupt capability that is not a pa rt of the IEEE 802.3 specification. This
interrupt capability generates an active low asynchronous in terrupt signal on the nINT output whenever certain events
are detected as setup by the Interrupt Mask Register.
The device’s interrupt system provides two modes, a Primary Interrupt mode and an Alternative interrupt mode. Both
systems will assert the nINT pin low when the corresponding mask bit is set. These mo des differ only in how they de-
assert the nINT interrupt output. These modes are detailed in the following subsectio ns.
Note: The Primary interrupt mode is the default interrupt mode after a power-up or hard reset. The Alternative
interrupt mode requires setup after a power-up or hard reset.
3.6.1 PRIMARY INTERRUPT SYSTEM
The Primary interrupt system is the default interrupt mode (ALTINT bit of the Mode Control/Status Register is “0”). The
Primary interrupt system is always selected after power-up or hard reset. In this mode, to set an interrupt, set the cor -
responding mask bit in the Interrupt Mask Register (see Table 3-3). Then when the event to assert nINT is true, the nINT
output will be asserted. When the corresponding event to deassert nINT is true, then the nINT will be de-asserted.
TABLE 3-2: INTERRUPT MANAGEMENT TABLE
Mask Interrupt Source Flag Interrupt Source Event to Assert
nINT Event to
De-Assert nINT
30.7 29.7 ENERGYON 17.1 ENERGYON Rising 17.1
(Note 3-3)Falling 17.1 or
Reading register 29
30.6 29.6 Auto-Negotiation
complete 1.5 Auto-Negotiate
Complete Rising 1.5 Falling 1.5 or
Reading register 29
2016 Microchip Technology Inc. DS00002165B-page 25
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Note 3-1 If the mask bit is enabled and nINT has been de-asserted while ENERGYON is still high, nINT will
assert for 256 ms, approximately one second after ENERGYON goes low when the Cable is
unplugged. To prevent an unexpected assertion of nINT, the ENERGYON interrupt mask should
always be cleared as part of the ENERGYON interrupt service routine.
Note: The ENERGYON bit in the Mode Control/St atus Register is defaulted to a ‘1’ at the start of the signal acqui-
sition process, therefore the INT7 bit in the Interrupt Mask Register will also read as a ‘1’ at power-up. If no
signal is present, then both ENERGYON and INT7 will clear within a few milliseconds.
3.6.2 ALTERNATE INTERRUPT SYSTEM
The Alternate interrupt system is enabled by setting the ALTINT bit of the Mode Control/Status Register to “1”. In this
mode, to set an interrupt, set the corresponding bit of the in the Mask Register 30, (see Table 3-4). To Clear an interrupt,
either clear the corresponding bit in the Interrupt Mask Register to deassert the nINT output, or clear the interrupt
source, and write a ‘1’ to the corresponding Interrupt Source Fla g. Writing a ‘1’ to the Interrupt Source Flag will cause
the state machine to check the Interrupt Source to determine if the Interrupt Source Flag should clear or stay as a ‘1’. If
the Condition to deassert is true, then the Interrupt Source Flag is cleared and nINT is also deasserted. If the Condition
to deassert is false, then the Interrupt Source Flag remains set, and the nINT remains asserted.
30.5 29.5 Remote Fault
Detected 1.4 Remote Fault Rising 1.4 Falling 1.4, or
Reading register 1 or
Reading register 29
30.4 29.4 Link Down 1.2 Link Status Falling 1.2 Reading register 1 or
Reading register 29
30.3 29.3 Auto-Negotiation
LP Acknowledge 5.14 Acknowledge Rising 5.14 Falling 5.14 or
Read register 29
30.2 29.2 Parallel Detection
Fault 6.4 Parallel Detec-
tion Fault Rising 6.4 Falling 6.4 or
Reading register 6, or
Reading register 29
or
Re-Auto Negotiate or
Link down
30.1 29.1 Auto-Negotiation
Page Received 6.1 Page Received Rising 6.1 Falling of 6.1 or
Reading register 6, or
Reading register 29
Re-Auto Negotiate, or
Link Down.
TABLE 3-2: INTERRUPT MANAGEMENT TABLE
LAN8720A/LAN8720AI
DS00002165B-page 26 2016 Microchip Technology Inc.
For example, setting the INT7 bit in the Interrupt Mask Register wi ll enable the ENERGYON i nterrupt. After a cable is
plugged in, the ENERGYON bit in the Mode Control/Status Register goes active an d nINT will be asserted l ow. To de-
assert the nINT interrupt output, either clear the ENERGYON bit in the Mode Control/Status Register by removing the
cable and then writing a ‘1’ to the INT7 bit in the Interrupt Mask Register, OR clear the INT7 mask (bit 7 of the Interrupt
Mask Register).
TABLE 3-3: ALTERNATIVE INTERRUPT SYSTEM MANAGEMENT TABLE
Mask Interrupt Source Flag Interrupt Source Event to
Assert nINT Condition to
De-Assert
Bit to
Clear
nINT
30.7 29.7 ENERGYON 17.1 ENERGYON Rising 17.1 17.1 low 29.7
30.6 29.6 Auto-Negotiation
complete 1.5 Auto-Negotiate
Complete Rising 1.5 1.5 low 29.6
30.5 29.5 Remote Fault
Detected 1.4 Remote Fault Rising 1.4 1.4 low 29.5
30.4 29.4 Link Down 1.2 Link Status Falling 1.2 1.2 high 29.4
30.3 29.3 Auto-Negotiation
LP Acknowledge 5.14 Acknowledge Rising 5.14 5.14 low 29.3
30.2 29.2 Parallel Detec-
tion Fault 6.4 Parallel Detec-
tion Fault Rising 6.4 6.4 low 29.2
30.1 29.1 Auto-Negotiation
Page Received 6.1 Page Received Rising 6.1 6.1 low 29.1
Note: The ENERGYON bit in the Mode Control/S t atus Register is defaulted to a ‘1’ at the start of the signal acqui-
sition process, therefore the INT7 bit in the Interrupt Mask Register will also read as a ‘1’ at power-up. If no
signal is present, then both ENERGYON and INT7 will clear within a few milliseconds.
3.7 Configuration Straps
Configuration straps allow various features of the device to be automatically configured to user defined values. Config-
uration straps are latched upon Power-On Reset (POR) and pin reset (nRST). Configuration straps include internal
resistors in order to prevent the signal from floatin g whe n unconn ected. If a particular configur ation strap is connected
to a load, an external pull-up or pull-down resistor should be used to augment the internal resistor to ensure that it
reaches the required voltage level prior to latching. The internal resistor ca n also be overridden by the addition of an
external resistor.
Note 3-2 The system designer must guarantee that configuration strap pins meet the timing requirements
specified in Section 5.5.3, "Power-On nRST & Configuration Strap Timing," on page 59. If
configuration strap pins are not at the correct voltage level prior to being latched, the device may
capture incorrect strap values.
Note 3-3 When externally pulling configuration straps high, the strap should be tied to VDDIO, except for
REGOFF and nINTSEL which should be tied to VDD2A.
3.7.1 PHYAD[0]: PHY ADDRESS CONFIGURATION
The PHY AD0 bit is driven high or low to give each PHY a unique address. This address is latched into an internal register
at the end of a hardware reset (default = 0b). In a multi-PHY applica tion (such as a repeater), the con troller is able to
manage each PHY via the unique address. Each PHY checks each management data frame for a matching address in
the relevant bits. When a match is recognized, the PHY responds to that particular frame. The PHY address is also used
to seed the scrambler. In a multi-PHY application, this ensures tha t the scramblers are ou t of synch ronizatio n and dis-
perses the electromagnetic radiation across the frequency spectrum.
2016 Microchip Technology Inc. DS00002165B-page 27
LAN8720A/LAN8720AI
The device’s SMI address may be configured using hardware configuration to either the value 0 or 1. The user can con-
figure the PHY address using Software Configuration if an address greater than 1 is required. The PHY address can be
written (after SMI communication at some address is established) using the PHYAD bit s of the Special Modes Register.
The PHYAD0 hardware configuration strap is multiplexed with the RXER pin.
3.7.2 MODE[2:0]: MODE CONFIGURATION
The MODE[2:0] configuration straps control the confi guration of the 10/100 digital block. Wh en the nRST pin is deas -
serted, the register bit values are loaded accord ing to the MODE[2:0] configuration straps. The 10/100 dig ital block is
then configured by the register bit values. When a soft reset occurs via the Soft Reset bit of the Basic Control Register,
the configuration of the 10/100 digital block is controlled by the register bit values and the MODE[2:0] configuration
straps have no affect.
The device’s mode may be con figured using the hardware co nfiguration straps as su mmarized in Table 3-6. The user
may configure the transceiver mode by writin g the SMI registers.
TABLE 3-4: MODE[2:0] BUS
MODE[2:0] Mode Definitions
Default Register Bit Values
Register 0 Register 4
[13,12,10,8] [8,7,6,5]
000 10Base-T Half Duplex. Auto-negotiation disabled. 0000 N/A
001 10Base-T Full Duplex. Auto-negotiation disabled. 0001 N/A
010 100Base-TX Half Duplex. Auto-negotiation di s-
abled.
CRS is active during Transmit & Receive.
1000 N/A
011 100Base-TX Full Duplex. Auto-negotiation disabled.
CRS is active during Receive. 1001 N/A
100 100Base-TX Half Duplex is advertised. Auto-negoti-
ation enabled.
CRS is active during Transmit & Receive.
1100 0100
101 Repeater mode. Auto-nego tiation enabled.
100Base-TX Half Duplex is advertised.
CRS is active during Receive.
1100 0100
110 Power Down mode. In this mode the transceiver will
wake-up in Power-Down mode. The transceiver
cannot be used when the MODE[2:0] bits are set to
this mode. To exit this mode, the MODE bits in Reg-
ister 18.7:5(see Section 4.2.9, "Special Modes Reg-
ister," on page 50) must be configured to some
other value and a soft reset must be issued.
N/A N/A
111 All capable. Auto-negotiation enabled. X10X 1111
The MODE[2:0] hardware configuration pins are multiplexed with other signals as shown in Table 3-5.
TABLE 3-5: PIN NAMES FOR MODE BITS
MODE Bit Pin Name
MODE[0] RXD0/MODE0
MODE[1] RXD1/MODE1
LAN8720A/LAN8720AI
DS00002165B-page 28 2016 Microchip Technology Inc.
3.7.3 REGOFF: INTERNAL +1.2V REGULATOR CONFIGURATION
The incorporation of flexPWR technology provides the ability to disable the internal +1.2V regulator . When the regulator
is disabled, an external +1.2V must be supplied to the VDDCR pin. Disabling the internal +1.2V regulator makes it pos-
sible to reduce total system power , since an external switching regulator with greater efficiency (versus the internal linear
regulator) can be used to provide +1.2V to the transceiver circuitry.
Note: Because the REGOFF configuration strap shares functionality with the LED1 pin, proper consideration must
also be given to the LED polarity. Refer to Section 3.8.1.1, "REGOFF and LED1 Polarity Selection," on
page 33 for additional information on the relation between REGOFF and the LED1 polarity.
3.7.3.1 Disabling the Internal +1.2V Regulator
To disable the +1.2V internal regulator, a pull-up strapping resistor should be connected from the REGOFF configuration
strap to VDD2A. At power-on, after both VDDIO and VDD2A are within specification, the transceiver will sample
REGOFF to determine whether the internal regulator should turn on. If the pin is sampled at a voltage greater than VIH,
then the intern al regula tor is di sable d and the system must sup ply +1.2V to the VDDCR pin . The VDDIO vo ltage must
be at least 80% of the operating voltage level (1.44V when operating at 1.8V, 2.0V when operating at 2.5V, 2.64V when
operating at 3.3V) before voltage is applied to VDDCR. As describe d in Section 3.7.4.2, when REGOFF is left floating
or connected to VSS, the internal regulator is enabled and the system is not required to supply +1.2V to the VDDCR pin.
3.7.3.2 Enabling the Internal +1.2V Regulator
The +1.2V for VDDCR is supplied by the on-chip regulator unless the transceiver is configured for the regulator off mode
using the REGOFF configuration strap as described in Section 3.7.4.1. By default, the internal +1.2V regulator is
enabled when REGOFF is floating (due to the internal pull-down resistor). During power-on, if REGOFF is sampled
below VIL, then the internal +1.2V regulator will turn on and operate with power from the VDD2A pin .
3.7.4 NINTSEL: NINT/REFCLKO CONFIGURATION
The nINTSEL configuration strap is used to select between one of two available modes: REF_CLK In Mode (nINT) and
REF_CLK Out Mode. The configured mode determines the function of the nINT/REFCLKO pin. The nINTSEL configu-
ration strap is latched at POR and on the rising edge of the nRST. By default, nINTSEL is configured for nINT mode via
the internal pull-up resistor.
TABLE 3-6: NINTSEL CONFIGURATION
Strap Value Mode REF_CLK description
nINTSEL = 0 REF_CLK Out Mode nINT/REFCLKO is the source of REF_CLK.
nINTSEL = 1 REF_CLK In Mode nINT/REFCLKO is an active low interrupt output.
The REF_CLK is sourced externally and must be driven
on the XTAL1/CLKIN pin.
The RMII REF_CLK is a continuous clock that provides the timing reference for CRS_ DV, RXD[1:0], TXEN, TXD[1:0]
and RXER. The device uses REF_CLK as the network clock such that no buffering is required on the transmit data path.
However, on the receive data path, the receiver recovers the clock from the incoming data stream. The device uses
elasticity buffering to accommodate for differences between the recovered clock and the local REF_CLK.
In REF_CLK In Mode, th e 50MHz REF_C LK is dri ven on the XTAL1/CLKIN pin. This is the tradi tional system con figu -
ration when using RMII, and is described in Section 3.7.4.1. When configured for REF_CLK Out Mode, the device gen-
erates the 50MHz RMII REF_CLK and the nINT interrupt is not available. REF_CLK Out Mode allows a low-cost 25MHz
crystal to be used as the reference for REF_CLK. This configuration may result in reduced system cost and is described
in Section 3.7.4.2.
MODE[2] CRS_DV/MODE2
TABLE 3-5: PIN NAMES FOR MODE BITS
MODE Bit Pin Name
2016 Microchip Technology Inc. DS00002165B-page 29
LAN8720A/LAN8720AI
Note: Because the nINTSEL configuration strap shares functionality with the LED2 pin, proper consideration must
also be given to the LED polarity. Refer to Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection," on
page 33 for additional information on the relation between nINTSEL and the LED2 polarity.
3.7.4.1 REF_CLK In Mode
In REF_CLK In Mode, th e 50MHz REF_CLK is driven on the XTAL1/CLKIN pin. A 50MHz source for REF_CLK must
be available external to the device when using th is mode. The clock is driven to both the MAC and PHY as shown in
Figure 3-7.
FIGURE 3-7: EXTERNAL 50MHZ CLOCK SOURCES THE REF_CLK
LAN8720A/LAN8720Ai
10/100 PHY
24-QFN
RMII
TXP
TXN
Mag RJ45
RXP
RXN
XTAL1/CLKIN
XTAL2
TXD[1:0]
2
RXD[1:0]
CRS_DV
2
RMII
LED[2:1]
2
Interface
MDIO
MDC
nINT
nRST
TXEN
MAC
Accepts external
50MHz clock
50MHz
Reference
Clock
All RMII signals are
synchronous to the supplied
clock
REF_CLK RXER
3.7.4.2 REF_CLK Out Mode
To reduce BOM cost, the device includes a feature to generate the RMII REF_CLK signal from a low-cost, 25MHz fun-
damental crystal. This type of crystal is inexpensive in comparison to 3rd overtone crystals that would normally be
required for 50MHz. The MAC must be capable of operating with an external clock to take advantage of this feature as
shown in Figure 3-8.
In order to optimize package size and cost, the REFCLKO pin is multiplexed with the nINT pin. In REF_CLK Out mode,
the nINT functionality is disabled to ac commodate usage of REFCLKO as a 50MHz clock to the MAC.
Note: The REF_CLK Out Mode is not part of the RMII Specification. T iming in this mode is not compliant with the
RMII specification. To ensure proper system operation, a timing analysis of the MAC and LAN8720 must be
performed.
FIGURE 3-8: SOURCING REF_CLK FROM A 25MHZ CRYSTAL
LAN8720A/LAN8720Ai
10/100 P H Y
24-QFN
RMII
TXP
TXN
Mag RJ45
RXP
RXN
25MHz
XTAL1/CLKIN
XTAL2
LED[2:1]
2
Interface
nRST
TXD[1:0]
2
RXD[1:0]
CRS_DV
2
RMII MDIO
MDC
TXEN
REFCLKO
MAC
Capable of
accepting 50MHz
clock
Note: nINT not available in
this configuration
RXER
REF_CLK
LAN8720A/LAN8720AI
DS00002165B-page 30 2016 Microchip Technology Inc.
In some system architectures, a 25MHz clock source is availab le. The device can be used to generate the REF_CLK
to the MAC as shown in FIGURE 3-9:. It is important to note that in this specific example, only a 25MHz clock can be
used (clock cannot be 50MHz). Similar to the 25MHz crystal mode, the nINT function is disabled.
FIGURE 3-9: SOURCING REF_CLK FROM EXTERNAL 25MHZ SOURCE
LAN8720A/LAN8720Ai
10/100 PHY
24-QFN
RMII
TXP
TXN
Mag RJ45
RXP
RXN
XTAL1/CLKIN
XTAL2
TXD[1:0]
2
RXD[1:0]
CRS_DV
2
RMII
LED[2:1]
2
Interface
MDIO
MDC
nRST
TXEN
REFCLKO
MAC
Capable of
accepting 50MHz
clock
Note: nINT is not availa ble in
this configuration
RXER
25MHz
Clock
REF_CLK
2016 Microchip Technology Inc. DS00002165B-page 31
LAN8720A/LAN8720AI
3.8 Miscellaneous Functions
3.8.1 LEDS
T wo LED signals are provided as a convenient means to determine the transceiver's mode of operation. All LED signals
are either active high or active low as described in Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection" and Section
3.8.1.1, "REGOFF and LED1 Pola rity Selection," on page 33.
The LED1 output is driven active whenever the device detects a valid link, and blinks when CRS is active (high) indicat-
ing activity.
The LED2 output is driven acti ve when the operating spee d is 100Mbps. This LED will go ina ctive when the operating
speed is 10Mbps or during line isolation.
Note: When pulling the LED1 and LED2 pins high , they must be tied to VDD2A, NOT VDDIO.
LAN8720A/LAN8720AI
DS00002165B-page 32 2016 Microchip Technology Inc.
3.8.1.1 REGOFF and LED1 Polarity Selection
The REGOFF configuration strap is shared with the LED1 pin. The LED1 output will automatically change polarity based
on the presence of an external p ull-up resistor. If the LED 1 pi n is pulled high to VDD2A b y an externa l pull-up resistor
to select a logical high for REGOFF, then the LED1 output will be active low. If the LED1 pin is pulled low by the internal
pull-down resistor to select a log ical low for REGOFF, the LED1 output will then be an active high output. Figure 3-7
details the LED1 polarity for each REGOFF configuration.
FIGURE 3-10: LED1/REGOFF POLARITY CONFIGURATION
LED1/REGOFF
~270 ohms
REGOFF = 0 (Regulator ON)
LED output = Active High
~270 ohms
VDD2A
REGOFF = 1 (Regulator OFF)
LED output = Active Low
LED1/REGOFF
10K
Note: Refer to Section 3.7.4, "REGOFF: Internal +1.2V Regu lator Configuration," on page 32 for additional infor-
mation on the REGOFF configuration strap.
3.8.1.2 nINTSEL and LED2 Polarity Selection
The nINTSEL configuration strap is shared with the LED2 pin. The LED2 output will automatically change polarity based
on the presence of an external pu ll-down resistor. If the LED2 pin is pulled high to VDD2A to sele ct a logical high for
nINTSEL, then the LED2 output will be active low . If the LED2 pin is pulled low by an external pull-down resistor to select
a logical low for nINTSEL, the LE D2 output will then be an active high output. Figure 3-8 details the LED2 polarity for
each nINTSEL configuration.
FIGURE 3-11: LED2/NINTSEL POLARITY CONFIGURATION
~270 ohms
nINTSEL = 0
LED output = Active High
10K
~270 ohms
VDD2A
nINTSEL = 1
LED output = Active Low
LED2/nINTSEL
LED2/nINTSEL
Note: Refer to Section 3.7.5, "nINTSEL: nINT/TXER/TXD4 Configuration," on page 32 for additional in formation
on the nINTSEL configuration strap.
2016 Microchip Technology Inc. DS00002165B-page 33
LAN8720A/LAN8720AI
3.8.2 VARIABLE VOLTAGE I/O
The device’s digital I/O pins are variable voltage, allowing them to take advantage of low power savings from shrinking
technologies. These pins can operate from a low I/O voltage of +1.62V up to +3.6V. The applied I/O voltage must main-
tain its value with a tolerance of ± 10%. Varying the voltage up or down after the transceiver has completed power-on
reset can cause errors in the transceiver operation. Refer to Section 5.0, "Operational Characteristics," on page 54 for
additional information.
Note: Input signals must not be driven high before power is applied to the device.
3.8.3 POWER-DOWN MODES
There are two device po wer-do wn modes: Ge neral Pow er-D own Mode and Ene rgy De te ct Power-Down Mode . These
modes are described in the following subsections.
3.8.3.1 Ge ner al Pow er -D own
This power-down mode is controlled via the Power Down bit of the Basic Control Register. In this mode, the entire trans-
ceiver (except the management interface) is powered-down and remains in this mode as long as the Power Down bit is
“1”. When the Power Down bit is cleared, the tran sceiver powers up and is automatically reset.
3.8.3.2 Energy Detect Power-Down
This power-down mode is activated by setting the EDPWRDOWN bit of the Mode Control/S tatus Register. In this mode,
when no energy is present on the line the transceiver is powered down (except for the management interface, the
SQUELCH circuit, and the ENERGYON logic). The ENERGYON logic is used to detect the presence of valid en ergy
from 100BASE-TX, 10BASE-T, or Auto-negotiation signals.
In this mode, when the ENERGYON bit of the Mode Control/Status Register is low, the transceiver is powered-down
and nothing is transmi tted. When energ y is recei ved via lin k pulses or packets, the ENERGYON bit goe s high and the
transceiver powers-up. The device automatically resets into the state prior to power-down and asserts the nINT interrupt
if the ENERGYON interrupt is enabled in the Interrupt Mask Register. The first and possibly the second packet to acti-
vate ENERGYON may be lost.
When the EDPWRDOWN bit of the Mode Control/Status Register is low, energy detect power-down is disabled.
3.8.4 ISOLA TE M ODE
The device data paths may be electrically isolated from the RMII interface by setting the Isolate bit of the Basic Control
Register to “1”. In isolation mode, the transceiver does not respond to the TXD, TXEN and TXER inputs, but does
respond to management transactions.
Isolation provides a means for multiple transceivers to be connected to the same RMII interface without contention. By
default, the transceiver is not isolated (on power-up (Isolate=0).
3.8.5 RESETS
The device provides two forms of reset: Hardware and Software. The device registers are reset by both Hardware and
Software reset s. Select register bits, indicated as “NASR” in the register definitions, are not cleared by a Software reset.
The registers are not reset by the power-down modes described in Section 3.8.3.
Note: For the first 16us after coming out of reset, the RMII interface will run at 2.5 MHz. After this time, it will switch
to 25 MHz if auto-negotiation is enabled.
3.8.5.1 Hardware Reset
A Hardware reset is asserted by driving the nRST input pin low . When driven, nRST should be held low for the minimum
time detailed i n Section 5.5.3, "Power-On nRST & Confi guration Strap Timing," on page 59 to ensure a proper trans-
ceiver reset. During a Hardware reset, an external clock must be supplied to the XTAL1/CLKIN signal.
Note: A hardware reset (nRST assertion) is required following power-up. Refer to Section 5.5.3, "Power-On nRST
& Configuration Strap Timing," on page 59 fo r additional information.
3.8.5.2 Software Reset
A Software reset is activated by setting the Soft Reset bit of the Basic Control Register to “1”. All registers bits, except
those indicated as “NASR” in the register definitions, are cleared by a Software reset. The Soft Reset bit is self-clearing.
Per the IEEE 802.3u standard, clause 22 (22.2.4.1.1 ) the reset process will be completed within 0 .5s from the setting
of this bit.
LAN8720A/LAN8720AI
DS00002165B-page 34 2016 Microchip Technology Inc.
3.8.6 CARRIER SENSE
The carrier sense (CRS) is output on the CRS_DV pin. CRS is a signal defined by the MII specification in the IEEE
802.3u standard. The device asserts CRS based only on receive activity whenever the transceiver is either in repeater
mode or full-duplex mode. Otherwise the transceiver asserts CRS based on either transmit or receive activity.
The carrier sense logic uses the encoded, unscrambled data to determine carrier activity status. It activates carrier
sense with the detection of 2 non-contiguous zeros within any 10 bit span. Carrier sense terminates if a span of 10 con-
secutive ones is detected before a /J/K/ Start-of Stream Delimiter pair. If an SSD pair is detected, carrier sense is
asserted until either /T/R/ End–of-Stream Delimiter pair or a pair of IDLE symbols is d etected. Carrier is negated a fter
the /T/ symbol or the first IDLE. If /T/ is not followed by /R/, then carrier is maintained. Carrier is treated similarly for IDLE
followed by some non-IDLE symbol.
3.8.7 LINK INTEGRITY TEST
The device performs the link integrity test as outlined in the IEEE 802.3u (Clause 24-15) Link Monitor state diagram.
The link status is multiplexed with the 10Mbps link status to form the Link Status bit in the Basic Status Register and to
drive the LINK LED (LED1).
The DSP indicates a valid MLT-3 waveform present on the R XP and RXN signals as d efined by the ANSI X3.2 63 TP-
PMD standard, to the Link Monitor state-machine, using the internal DATA_VALID signal. When DATA_VALID is
asserted, the control logic moves into a Link-Ready state and waits for an enable from the auto-negotiation block. When
received, the Link-Up state is entered, and the Transmit and Receive logic blo cks become active. Should auto-ne goti-
ation be disabled, the link integrity logic moves immediately to the Link-Up state when the DATA_VALID is asserted.
To allow the line to stabilize, the link integrity logic will wait a minimum of 330 sec from the time DATA_VALID is
asserted until the Link-Ready state is entered. Should the DATA_VALID input be negated at any time, this logic will
immediately negate the Link signal and enter the Link-Down state.
When the 10/100 digital block is in 10BASE-T mode, the link status is derived from the 10BASE-T receiver logic.
3.8.8 LOOPBACK OPERATION
The device may be configure d for near-e nd loopback and far loop back. These lo opback mode s are de tailed in the fol -
lowing subsections.
3.8.8.1 Near-end Loopback
Near-end loopback mode sends the digital transmit data back out the receive data signals for testing purposes, as indi-
cated by the blue arrows in Figure 3-9. The near-end loopback mode is enabled by setting the Loopback bit of the Basic
Control Re gister to “1”. A large percentage of the digital circuitry is operational in near-end loopback mode because data
is routed through the PCS and PMA layers into the PMD sublayer before it is looped back. The transmitters are powered
down regardless of the state of TXEN.
FIGURE 3-12: NEAR-END LOOPBACK BLOC K DIAGRAM
SMSC
Ethernet Transceiver
10/100
Ethernet
MAC
CAT-5
XFMR
Digital
RXD
TXD
Analog
RX
TX
X
X
2016 Microchip Technology Inc. DS00002165B-page 35
LAN8720A/LAN8720AI
3.8.8.2 Far Loopback
Far loopback is a specia l test mode for MDI (analog) l oopback as indicated by the b lue arrows in Figure 3-11. The far
loopback mode is enabled by se tting th e FARLOOPBACK bit of the Mode Control/Status Register to “1”. In this mode,
data that is received from the link partner on the MDI is looped back out to the link partner. The digital interface signals
on the local MAC interface are isolated.
FIGURE 3-13: FAR LOOPBACK BLOCK DIAGRAM
Far-end system
SMSC
Ethernet Transceiver
10/100
Ethernet
MAC
CAT-5
XFMR
Digital
RXD
TXD
Analog
RX
TX Link
Partner
X
X
3.8.8.3 C o nn e ctor Loopbac k
The device maintains reliable transmission over very short cables, and can be tested in a connector loopback as shown
in Figure 3-11. An RJ45 loopback cable can be used to route the transmit signals an the output of the transformer back
to the receiver inputs, and this loopback will work at both 10 and 100.
FIGURE 3-14: CONNECTOR LOOPBACK BLOCK DIAGRAM
SMSC
Ethernet Transceiver
10/100
Ethernet
MAC XFMR
Digital
RXD
TXD
Analog
RX
TX 1
2
3
4
5
6
7
8
RJ45 Loopback Cable .
Created by connecting pin 1 to pin 3
and connectin g pin 2 to pin 6.
3.9 Application Diagrams
This section provides typical application diagrams for the following:
•Simplified System Level Application Diagram
•Power Supply Diagram (1.2V Supplied by Internal Regulator)
•Power Supply Diagram (1.2V Supplied by External Source)
•Twisted-Pair Interface Diagram (Single Power Suppl y)
•Twisted-Pair Interface Diagram (Dual Power Supplies)
LAN8720A/LAN8720AI
DS00002165B-page 36 2016 Microchip Technology Inc.
3.9.1 SIMPLIFIED SYSTEM LEVEL APPLICATION DIAGRAM
FIGURE 3-15: SIMPLIFIED SYSTEM LEVEL APPLICATION DIAGRAM
LAN8720A/LAN8720Ai
10/100 PHY
24-QFN
RMII
TXP
TXN
Mag RJ45
RXP
RXN
25MHz
XTAL1/CLKIN
XTAL2
TXD[1:0]
2
RXD[1:0]
RXER
2
RMII
LED[2:1]
2
Interface
MDIO
MDC
nINT
nRST
TXEN
2016 Microchip Technology Inc. DS00002165B-page 37
LAN8720A/LAN8720AI
3.9.2 POWER SUPPLY DIAGRAM (1.2V SUPPLIED BY INTERNAL REGULATOR)
FIGURE 3-16: POWER SUPPLY DIAGRAM (1.2V SUPPLIED BY INTERNAL REGULATOR)
LAN8720A/LAN8720Ai
24-QFN
RBIAS
VSS 12.1k
VDD2A
CBYPASS
CBYPASS
VDD1A
VDDIO
CBYPASS
CF
VDDDIO
Supply
1.8 - 3.3V
Power
Supply
3.3V
VDDCR
LED1/
REGOFF
~270 Ohm
Core Logic
Internal
Regulator
Ch.2 3.3V
Circuitry
INOUT
Ch.1 3.3V
Circuitry
470 pF
1 uF
LAN8720A/LAN8720AI
DS00002165B-page 38 2016 Microchip Technology Inc.
3.9.3 POWER SUPPLY DIAGRAM (1.2V SUPPLIED BY EXTERNAL SOURCE)
FIGURE 3-17: POWER SUPPLY DIAGRAM (1.2V SUPPLIED BY EXTERNAL SOURCE)
LAN8720A/LAN8720Ai
24-QFN
RBIAS
VSS 12.1k
VDD2A
CBYPASS
CBYPASS
VDD1A
VDDIO
CBYPASS
CF
VDDDIO
Supply
1.8 - 3.3V
Power
Supply
3.3V
VDDCR
LED1/
REGOFF
Core Logic
Intern al
Regulator
(Disabled)
Ch.2 3.3V
Circuitry
INOUT
Ch.1 3.3V
Circuitry
VDDCR
Supply
1.2V
~270 Ohm
10k
470 pF
1 uF
2016 Microchip Technology Inc. DS00002165B-page 39
LAN8720A/LAN8720AI
3.9.4 TWISTED-PAIR INTERFACE DIAGRAM (SINGLE POWER SUPPLY)
FIGURE 3-18: TWISTED-PAIR INTERFACE DIAGRAM (SINGLE POWER SUPPLY)
Magnetics
LAN8720A/LAN8720Ai
24-QFN
VDD2A CBYPASS
TXP
TXN
Power
Supply
3.3V
1
2
3
4
5
6
7
8
1000 pF
3 kV
RJ45
75
75
RXP
RXN
CBYPASS
VDD1A CBYPASS
49.9 Ohm Resistors
Ferrite
bead
LAN8720A/LAN8720AI
DS00002165B-page 40 2016 Microchip Technology Inc.
3.9.5 TWISTED-PAIR INTERFACE DIAGRAM (DUAL POWER SUPPLIES)
FIGURE 3-19: TWISTED-PAIR INTERFACE DIAGRAM (DUAL POWER SUPPLIES)
Magnetics
LAN8720A/LAN8720Ai
24-QFN
VDD2A CBYPASS
TXP
TXN
Power
Supply
3.3V
1
2
3
4
5
6
7
8
1000 pF
3 kV
RJ45
75
75
RXP
RXN
CBYPASS
VDD1A CBYPASS
49.9 Ohm Resistors Power
Supply
2.5V - 3.3V
2016 Microchip Technology Inc. DS00002165B-page 41
LAN8720A/LAN8720AI
4.0 REGISTER DESCRIPTIONS
This chapter describes the various control and status registers (CSRs). All registers follow the IEEE 802.3 (clause
22.2.4) management register set. All functionality and bit definitions comply with these standards. The IEEE 802.3 spec-
ified register index (in decimal) is included with each reg ister definition, allowing fo r addressing of these registers via
the Serial Management Interface (SMI) protocol.
4.1 Register Nomenclature
Table 4-1 describes the register bit attribute notation used throughout this document.
TABLE 4-1: REGISTER BIT TYPES
Register Bit Type
Notation Register Bit Description
RRead: A register or bit with this attribute can be read.
WRead: A register or bit with this attribute can be written.
RO Read only: Read only. Writes have no effect.
WO Write only: If a register or bit is write-only, reads will return unspecified data.
WC Write One to Clear: writing a one clears the value. Writing a zero has no effect
WAC Write Anything to Clear: writing anything clears the value.
RC Read to Clear: Contents is cleared after the read. Writes have no effect.
LL Latch Low: Clear on read of register.
LH Latch High: Clear on read of register.
SC Self-Clearing: Contents are self-cleared after the being set. Writes of zero have no
effect. Contents can be read.
SS Self-Setting: Contents are self-setting after being cleared. Writes of one have no
effect. Contents can be read.
RO/LH Read Only, Latch High: Bit s with this at tribute will st ay high until the bit is read. After it
is read, the bit will either remain high if the high condition remains, or will go low if the
high condition has been removed. If the bit has not been read, the bit will remain high
regardless of a change to the high condition. This mode is used in some Ethernet PHY
registers.
NASR Not Affected by Software Reset. The state of NASR bits do not change on assertion
of a software reset.
RESERVED Reserved Fiel d: Reserved fields must be written with zeros to ensu re future compati-
bility. The value of reserved bits is not guaranteed on a read.
Many of these register bit notations can be combined. Some examples of this are shown below:
•R/W: Can be written. Will return current setting on a read.
•R/WAC: Will return curren t se ttin g on a re ad . Writing anything clears th e bit.
4.2 Control and Status Registers
Table 4-2 provides a list of supported registers. Register details, including bit definitions, are provided in the proceeding
subsections.
TABLE 4-2: SMI REGISTER MAP
Register Index
(Decimal) Register Name Group
0Basic Control Register Basic
1Basic Status Register Basic
2PHY Identifier 1 Extended
3PHY Identifier 2 Extended
4Auto-Negotiation Advertisement Register Extended
5Auto-Negotiation Link Partner Ability Register Extended
6Auto-Negotiation Expansion Register Extended
17 Mode Control/Status Register Vendor-specific
18 Special Modes Vendor-specific
26 Symbol Error Counter Register Vendor-specific
27 Control / Status Indication Register Vendor-specific
29 Interrupt Source Register Vendor-specific
30 Interrupt Mask Regist er Vendor-specific
31 PHY Special Control/Status Register Vendor-specific
LAN8720A/LAN8720AI
DS00002165B-page 42 2016 Microchip Technology Inc.
4.2.1 BASIC CONTROL REGISTER
Index (In Decimal): 0Size: 16 bits
Bits Description Type Default
15 Soft Reset
1 = software reset. Bit is self-clearing. When setting this bit do not set other
bits in this register. The configuration (as described in Section 3.7.2,
MODE[2:0]: Mo de Con fig uratio n) is set from the register bit values, and not
from the mode pin s.
R/W
SC 0b
14 Loopback
0 = normal operation
1 = loopback mode
R/W 0b
13 Speed Select
0 = 10Mbps
1 = 100Mbps
Ignored if Auto-negotiation is enabled (0.12 = 1).
R/W Note 4-1
12 Auto-Negotiation Enable
0 = disable auto-negotiate process
1 = enable auto-negotiate process (overrides 0.13 and 0.8)
R/W Note 4-1
2016 Microchip Technology Inc. DS00002165B-page 43
LAN8720A/LAN8720AI
Note 4-1 The default value of this bit is determined by the MODE[2:0] configuration straps. Refer to
Section 3.7.2, MODE[2:0]: Mode Configuration for additional information.
4.2.2 BASIC STATUS REGISTER
Index (In Decimal): 1Size: 16 bits
11 Power Down
0 = normal operation
1 = General power down mode
The Auto-Negotiation Enable must be cleared before set ting the Power
Down.
R/W 0b
10 Isolate
0 = normal operation
1 = electrical isolation of PHY from the RMII
R/W 0b
9Restart Auto-Negotiate
0 = normal operation
1 = restart auto-negotiate process
Bit is self-clearing.
R/W
SC 0b
8Duplex Mode
0 = half duplex
1 = full duplex
Ignored if Auto-Negotiation is enabled (0.12 = 1).
R/W Note 4-1
7:0 RESERVED RO —
Bits Description Type Default
15 100BASE-T4
0 = no T4 ability
1 = T4 able
RO 0b
14 100BASE-TX Full Duplex
0 = no TX full duplex ability
1 = TX with full duplex
RO 1b
13 100BASE-TX Half Duplex
0 = no TX half duplex ability
1 = TX with half duplex
RO 1b
12 10BASE-T Full Duplex
0 = no 10Mbps with full duplex ability
1 = 10Mbps with full duplex
RO 1b
11 10BASE-T Half Duplex
0 = no 10Mbps with half duplex ability
1 = 10Mbps with half duplex
RO 1b
10 100BASE-T2 Full Duplex
0 = PHY not able to perform full duplex 100BASE-T2
1 = PHY able to perform full duplex 100BASE-T2
RO 0b
Bits Description Type Default
LAN8720A/LAN8720AI
DS00002165B-page 44 2016 Microchip Technology Inc.
4.2.3 PHY IDENTIFIER 1 REGISTER
Index (In Decimal): 2Size: 16 bits
Bits Description Type Default
15:0 PHY ID Number
Assigned to the 3rd through 18th bits of the Organizationally Unique Identifier
(OUI), respectively.
R/W 0007h
4.2.4 PHY IDENTIFIER 2 REGISTER
Index (In Decimal): 3Size: 16 bits
9100BASE-T2 Half Duplex
0 = PHY not able to perform half duplex 100BASE-T2
1 = PHY able to perform half dup lex 100BASE-T2
RO 0b
8Extended Status
0 = no extended status information in register 15
1 = extended status information in register 15
RO 0b
7:6 RESERVED RO —
5Auto-Negotiate Complete
0 = auto-negotiate process not completed
1 = auto-negotiate process completed
RO 0b
4Remote Fault
1 = remote fault condition detected
0 = no remote fault
RO/LH 0b
3Auto-Negotiate Ability
0 = unable to perform auto-negotiation function
1 = able to perform auto-negotiation function
RO 1b
2Link Status
0 = link is down
1 = link is up
RO/LL 0b
1Jabber Detect
0 = no jabber condition detected
1 = jabber condition detected
RO/LH 0b
0Extended Capabilities
0 = does not support extended capabilities registers
1 = supports extended capabilities registers
RO 1b
Bits Description Type Default
Bits Description Type Default
15:10 PHY ID Number
Assigned to the 19th through 24th bits of the OUI. R/W 110000b
9:4 Model Number
Six-bit manufacturer’s model number. R/W 001111b
3:0 Revision Number
Four-bit manufacturer’s revision number. R/W Note 4-2
2016 Microchip Technology Inc. DS00002165B-page 45
LAN8720A/LAN8720AI
Note 4-2 The default value of this field will vary dependent on the silicon revision number.
4.2.5 AUTO NEGOTIATION ADVERTISEMENT REGISTER
Index (In Decimal): 4Size: 16 bits
Bits Description Type Default
15:14 RESERVED RO —
13 Remote Fault
0 = no remote fault
1 = remote fault detected
R/W 0b
12 RESERVED RO —
11:10 Pause Operation
00 = No PAUSE
01 = Symmetric PAUSE
10 = Asymmetric PAUSE toward link partner
11 = Advertise support for both Symmetric PAUSE and Asymmetric PAUSE
toward lo c a l de v ic e
Note: When both Symmetric PAUSE and Asymmetric PAUSE are set,
the device will only be configured t o, at most, one of the two set-
tings upon auto-negotiation completion.
R/W 00b
9RESERVED RO —
8100BASE-TX Full Duplex
0 = no TX full duplex ability
1 = TX with full duplex
R/W Note 4-3
7100BASE-TX
0 = no TX ability
1 = TX able
R/W 1b
610BASE-T Full Duplex
0 = no 10Mbps with full duplex ability
1 = 10Mbps with full duplex
R/W Note 4-3
510BASE-T
0 = no 10Mbps ability
1 = 10Mbps able
R/W Note 4-3
LAN8720A/LAN8720AI
DS00002165B-page 46 2016 Microchip Technology Inc.
Note 4-3 The default value of this bit is determined by the MODE[2:0] configuration straps. Refer to
Section 3.7.2, MODE[2:0]: Mode Configuration for additional information.
4.2.6 AUTO NEGOTIATION LINK PARTNER ABILITY REGISTER
Index (In Decimal): 5Size: 16 bits
Bits Description Type Default
15 Next Page
0 = no next page ability
1 = next page capable
Note: This device does not support next page ability.
RO 0b
14 Acknowledge
0 = link code word not yet received
1 = link code word received from partner
RO 0b
13 Remote Fault
0 = no remote fault
1 = remote fault detected
RO 0b
12:11 RESERVED RO —
10 Pause Oper at io n
0 = No PAUSE supported by partner station
1 = PAUSE supported by partner station
RO 0b
9100BASE-T4
0 = no T4 ability
1 = T4 able
Note: This device does not support T4 ability.
RO 0b
8100BASE-TX Full Duplex
0 = no TX full duplex ability
1 = TX with full duplex
RO 0b
7100BASE-TX
0 = no TX ability
1 = TX able
RO 0b
610BASE-T Full Duplex
0 = no 10Mbps with full duplex ability
1 = 10Mbps with full duplex
RO 0b
510BASE-T
0 = no 10Mbps ability
1 = 10Mbps able
RO 0b
4:0 Selector Field
00001 = IEEE 802.3 RO 00001b
4:0 Selector Field
00001 = IEEE 802.3 R/W 00001b
Bits Description Type Default
2016 Microchip Technology Inc. DS00002165B-page 47
LAN8720A/LAN8720AI
4.2.7 AUTO NEGOTIATION EXPANSION REGISTER
Index (In Decimal): 6Size: 16 bits
Bits Description Type Default
15:5 RESER VED RO —
4Parallel Detection Fault
0 = no fault detected by parallel detection logic
1 = fault detected by parallel detection logic
RO/LH 0b
3Link Partner Next Page Able
0 = link partner does not have next page ability
1 = link partner has next page ability
RO 0b
2Next Page Able
0 = local device does not have next page ability
1 = local device has next page ability
RO 0b
1Page Received
0 = new page not yet received
1 = new page received
RO/LH 0b
0Link Partner Auto-Negotiation Able
0 = link partner does not have auto-negotiation ability
1 = link partner has auto-negotiation ability
RO 0b
4.2.8 MODE CONTROL/STATUS REGISTER
Index (In Decimal): 17 Size: 16 bits
Bits Description Type Default
15:14 RESERVED RO —
13 EDPWRDOWN
Enable the Energy Detect Power-Down mode:
0 = Energy Detect Power-Do wn is disabled
1 = Energy Detect Power-Down is enabled
R/W 0b
12:10 RESERVED RO —
9FARLOOPBACK
Enables far loopback mode (for exampl e, all the received packets are sent
back simultaneously (in 100BASE-TX only)). This mode works even if the Iso-
late bit (0.10) is set.
0 = Far loopback mode is disabled
1 = Far loopback mode is enabled
Refer to Section 3.8.9.2, Far Loopback for additional information.
R/W 0b
LAN8720A/LAN8720AI
DS00002165B-page 48 2016 Microchip Technology Inc.
4.2.9 SPECIAL MODES REGISTER
Index (In Decimal): 18 Size: 16 bits
Bits Description Type Default
15 RESERVED RO —
14 RESERVED
Write as 1, ignore on read. R/W
NASR 1b
13:8 RESERVED RO —
7:5 MODE
Transceiver mode of operation. Refer to Section 3.7.2, MODE[2:0]: Mode
Configuration for additional details.
R/W
NASR Note 4-5
4:0 PHYAD
PHY Address. The PHY Address is used for the SMI address and for initial-
ization of the Cipher (Scrambler) key. Refer to Section 3.7.1, PHYAD[ 2:0]:
PHY Address Configuration for additional details.
R/W
NASR Note 4-6
Note 4-4 The default value of this field is determined by the MODE[2:0] configuration straps. Refer to
Section 3.7.2, MODE[2:0]: Mode Configuration for additional information.
Note 4-5 The default value of this field is determined by the PHYAD[0] configuration strap. Refer to
Section 3.7.1, PHYAD[2:0]: PHY Address Configuration for additional information.
4.2.10 SYMBOL ERROR COUNTER REGISTER
Index (In Decimal): 26 Size: 16 bits
8:7 RESERVED RO —
6ALTINT
Alternate Interru p t M ode :
0 = Primary interrupt system enabled (Default)
1 = Alternate interrupt system enabled
Refer to Section 3.6, Interrupt Management for additi onal information.
R/W 0b
5:2 RESERVED RO —
1ENERGYON
Indicates whether energy is detected . This bit transitions to “0” if no valid
energy is detected within 256ms. It is reset to “1” by a hardware reset and is
unaf fe cted by a software reset. Ref er to Section 3.8.3.2, Energy Detect
Power-Down for additional information.
RO 1b
0RESERVED R/W 0b
Bits Description Type Default
Bits Description Type Default
15:0 SYM_ERR_CNT
The symbol error counter increments whenever an invalid code symbol is
received (including IDLE symbols) in 100BASE-TX mode. The counter is
incremented only once per packet, even when the received packet contains
more than one symbol error. This counter increments up to 65,536 (216) and
rolls over to 0 after reaching the maximum value.
Note: This register is cleared on reset , but is no t cl eared by re adi ng t he
register. This register does not increment in 10BASE-T mode.
RO 0000h
2016 Microchip Technology Inc. DS00002165B-page 49
LAN8720A/LAN8720AI
4.2.11 SPECIAL CONTROL/STATUS INDICATIONS REGISTER
Index (In Decimal): 27 Size: 16 bits
Bits Description Type Default
15 AMDIXCTRL
HP Auto-MDIX control:
0 = Enable Auto-MDIX
1 = Disable Auto-MDIX (use 27.13 to control channel)
R/W 0b
14 RESERVED RO —
13 CH_SELECT
Manual channel select:
0 = MDI (TX transmits, RX receives)
1 = MDIX (TX receives, RX transmit s )
R/W 0b
12 RESERVED RO —
11 SQEOFF
Disable the SQE test (Heartbeat):
0 = SQE test is enabled
1 = SQE test is disabled
R/W
NASR 0b
10:5 RESERVED RO —
4XPOL
Polarity state of the 10BASE-T:
0 = Normal polarity
1 = Reversed polarity
RO 0b
3:0 RESERVED RO —
4.2.12 INTERRUPT SOURCE FLAG REGISTER
Index (In Decimal): 29 Size: 16 bits
Bits Description Type Default
15:8 RESERVED RO —
7INT7
0 = not source of interrupt
1 = ENERGYON generated
RO/LH 0b
6INT6
0 = not source of interrupt
1 = Auto-Negotiation complete
RO/LH 0b
5INT5
0 = not source of interrupt
1 = Remote Fault Detected
RO/LH 0b
4INT4
0 = not source of interrupt
1 = Link Down (link status negated)
RO/LH 0b
3INT3
0 = not source of interrupt
1 = Auto-Negotiation LP Acknowledge
RO/LH 0b
2INT2
0 = not source of interrupt
1 = Parallel Dete ction Fault
RO/LH 0b
1INT1
0 = not source of interrupt
1 = Auto-Negotiation Page Received
RO/LH 0b
0RESERVED RO 0b
LAN8720A/LAN8720AI
DS00002165B-page 50 2016 Microchip Technology Inc.
4.2.13 INTERRUPT MASK REGISTER
Index (In Decimal): 30 Size: 16 bits
Bits Description Type Default
15:8 RESERVED RO —
7:1 Mask Bits
0 = interrupt source is masked
1 = interrupt source is enabled
Note: Refer to Section 4.2.12, In te rrupt Source Fl ag Regi ster fo r details
on the corresponding interrupt definitions.
R/W 0000000b
0RESERVED RO —
2016 Microchip Technology Inc. DS00002165B-page 51
LAN8720A/LAN8720AI
4.2.14 PHY SPECIAL CONTROL/STATUS REGISTER
Index (In Decimal): 31 Size: 16 bits
Bits Description Type Default
15:13 RESERVED RO —
12 Autodone
Auto-negotiation done indication:
0 = Auto-negotiation is not done or disabled (or not active)
1 = Auto-negotiation is done
RO 0b
11:5 RESERVED - Write as 0000010b, ignore on read. R/W 0000010b
4:2 Speed Indication
HCDSPEED value:
001 = 10BASE-T half-duplex
101 = 10BASE-T full-duplex
010 = 100BASE-TX half-duplex
110 = 100BASE-TX full-duplex
RO XXX
1:0 RESERVED RO —
LAN8720A/LAN8720AI
DS00002165B-page 52 2016 Microchip Technology Inc.
5.0 OPERATIONAL CHARACTERISTICS
5.1 Absolute Maximum Ratings*
Supply Voltage (VDDIO, VDD1A, VDD2A) (Note 5-1) ...............................................................................-0.5V to +3.6V
Digital Core Supply Voltage (VDDCR) (Note 5-1) ......................................................................................-0.5V to +1.5V
Ethernet Magnetics Supply Voltage ...........................................................................................................-0.5V to +3.6V
Positive voltage on signal pins, with respect to ground (Note 5-2)..............................................................................+6V
Negative voltage on signal pins, with respect to ground (Note 5-3)......................................................................... -0.5V
Positive voltage on XTAL1/CLKIN, with respect to ground ......................................................................................+3.6V
Positive voltage on XTAL2, with respect to ground..................................................................................................+2.5V
Ambient Operating Temperature in Still Air (TA)............................................................................................... Note 5-40
Storage Temperature............................................................................................................................. .-55oC to +15 0 oC
Junction to Ambient (JA)................................................................................................................................. .59.8oC/W
Junction to Case (JC)...................................................................................................................................... .12.6oC/W
Lead Temperature Range ...........................................................................................Refer to JEDEC Spec. J-STD-020
HBM ESD Performance per JEDEC JESD22-A114............................................................................................Class 3A
IEC61000-4-2 Contact Discharge ESD Performance (Note 5-5)............................................................................+/-8kV
IEC61000-4-2 Air-Gap Discharge ESD Performance (Note 5-5)..........................................................................+/-15kV
Latch-up Pe rfo rma nce per EIA/JESD 78........ .. ... ... ... ... .. ... ... ... ... .. ... ... ... ... .. ... ... ... ... .. ... ... ... ... .. ... ... ... ................. .+/-150mA
Note 5-1 When powering this device from labora tory or system power su pplies, it is important that the abso lute
maximum ratings not be exceeded or device failure can result. Some power supplies exhibit voltage
spikes on their outputs when AC power is switched on or off. In addition, voltage transients on the
AC power line may appear on the DC output. If this possibility exists, it is suggested that a clamp
circuit be used.
Note 5-2 This rating does not apply to the following pins: XTAL1/CLKIN, XTAL2, RBIAS.
Note 5-3 This rating does not apply to the following pins: RBIAS.
Note 5-4 0oC to +85oC for extended commercial version, -40oC to +85oC for industrial version.
Note 5-5 Performed by independent 3rd party test facility.
*Stresses exceeding those li sted in this section coul d cause permanent damage to the device. This is a st ress rating
only. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Functional
operation of the device at any condition exceeding those indicated in Section 5.2, "Ope rating Conditions**", Section 5.1,
"Absolute Maximum Rat ings*" , or any other ap plicable section of this specificat ion is not implied. No te, device sign als
are NOT 5 volt tolerant unless specified otherwise.
5.2 Operating Conditions**
Supply Voltage (VDD I O )....... ... ... ... ... ................... ... ... ... .. ... ... .................... .. ... ... ... ... .. ...............................+1.62V to +3.6V
Analog Port Supply Voltage (VDD1A, VDD2A).........................................................................................+3.0V to +3.6V
Digital Core Supply Voltage (VDDCR) ..................................................................................................+1.08V to +1.32V
Ethernet Magnetics Supply Voltage ........................................................................................................+2.25V to +3.6V
Ambient Operating Temperature in Still Air (TA)................................................................................................. Note 5-4
**Proper operation of the device is guaranteed only within the ranges specified in this section. After the device has com-
pleted power-up, VDDIO and the magnetics power supply must maintain their voltage level with +/-10%. Varying the
voltage greater than +/-10% after the device has completed power-up can cause errors in device operation.
Note: Do not drive input signals without power supplied to the device.
2016 Microchip Technology Inc. DS00002165B-page 53
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5.3 Power Consumption
This section details the device power measurements taken over various operating conditions. Unless otherwise noted,
all measurements were taken with power supplies at nominal values (VDDIO, VDD1A, VDD2A = 3.3V, VDDCR = 1.2V).
See Section 3.8.3, Power-Down Modes for a description of the power down modes. For more information on the REF_-
CLK modes, see Section 3.7.4, nINTSEL: nINT/REFCLKO Configuration.
5.3.1 REF_CLK IN MODE
TABLE 5-1: DEVICE ONLY CURRENT CONSUMPTION AND POWER DISSIPATION (REF_CLK IN
MODE)
Power Pin Group VDDA3.3
Power
PinS(mA)
VDDCR
Power
pin(mA)
VDDIO
power
pin(mA)
Total
Current
(mA)
Total
Power
(mW)
100BASE-TX /w traffic
Max 28 21 0.6 49 159
Typical 26 19 0.5 45 148
Min 23 18 0.3 41 96
Note 5-8
10BASE-T /w traffic
Max 9.7 13 0.6 24 77
Typical 8.9 12 0.5 22 70
Min 8.3 12 0.3 20 42
Note 5-8
Energy Detect Power Down
Max 4.2 3.0 0.2 7.4 25
Typical 4.1 1.9 0.2 6.2 21
Min 3.9 1.9 05.8 16
Note 5-8
General Power Down
Max 0.4 2.8 0.2 3.4 11.2
Typical 0.3 1.8 0.2 2.3 7.6
Min 0.3 1.7 0 2 3.0
Note 5-8
Note 5-6 The current at VDDCR is either supplied by the internal regulator from current entering at VDD2A,
or from an external 1.2V supply when the internal regulator is disabled.
Note 5-7 Current measurements do not include power applied t o the magnetics or the opt ional external LEDs.
The Ethernet component current is typically 41mA in 100BASE-TX mode and 100mA in 10BASE-T
mode, independent of the 2.5V or 3.3V supply rail of the transformer.
Note 5-8 Calculated with full flexPWR features activated: VDDIO=1.8V & internal regulator disabled.
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DS00002165B-page 54 2016 Microchip Technology Inc.
5.3.2 REF_CLK OUT MODE
TABLE 5-2: DEVICE ONLY CURRENT CONSUMPTION AND POWER DISSIPATION (REF_CLK
OUT MODE)
Power Pin Group VDDA3.3
Power
Pins(mA)
VDDCR
Power
Pin(mA)
VDDIO
Power
Pin(mA)
Total
Current
(mA)
Total
Power
(mW)
100BASE-T /w traffic
Max 28 20 6.3 54 179
Typical 26 19 5.8 50 164
Min 22 15 2.9 39 93
Note 5-11
10BASE-T /w traffic
Max 9.9 13 6.4 30 96
Typical 8.8 12 5.6 26 85
Min 7.1 10 3.0 20 41
Note 5-11
Energy Detect Power Down
Max 4.5 2.7 0.3 7.5 25
Typical 4.0 1.5 0.2 5.7 19
Min 3.9 1.2 05.1 15
Note 5-11
General Power Down
Max 0.4 2.5 0.2 3.1 10.2
Typical 0.4 1.3 0.2 1.9 6.3
Min 0.4 1.0 01.4 2.5
Note 5-11
.
Note 5-9 The current at VDDCR is either supplied by the internal regulator from current entering at VDD2A,
or from an external 1.2V supply when the internal regulator is disabled.
Note 5-10 Current measurements do no t include power applied to the magnetics or the optional external LEDs.
The Ethernet component current is typically 41mA in 100BASE-TX mode and 100mA in 10BASE-T
mode, independent of the 2.5V or 3.3V supply rail of the transformer.
Note 5-11 Calculated with full flexPWR features activated: VDDIO=1.8V & internal regulator disabled.
2016 Microchip Technology Inc. DS00002165B-page 55
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5.4 DC Specifications
TABLE 5-2: details the non-variable I/O buffer characteristics. These buffer types do not support variable voltage oper-
ation. TABLE 5-3: details the variable voltage I/O buffer characteristics. T y pical values are provided for 1.8V, 2.5V, and
3.3V VDDIO cases.
TABLE 5-3: NON-VARIABLE I/O BUFFER CHARACTERISTICS
Parameter Symbol Min Typ Max Units Notes
IS Type Input Buffer
Low Input Le ve l
High Input Level
Negative-Going Threshold
Positive-Going Threshold
Schmitt T rigger Hysteresis
(VIHT - VILT)
Input Leakage
(VIN = VSS or VDDIO)
Input Capacitance
VILI
VIHI
VILT
VIHT
VHYS
IIH
CIN
-0.3
1.01
1.39
336
-10
1.19
1.59
399
3.6
1.39
1.79
459
10
2
V
V
V
V
mV
uA
pF
Schmitt trigger
Schmitt trigger
Note 5-9
O12 Type Buffers
Low Output Level
High Output Level
VOL
VOH VDD2A -
0.4
0.4 V
V
IOL = 12mA
IOH = -12mA
ICLK Type Buffer
(XTAL1 Input)
Low Input Le ve l
High Input Level
VILI
VIHI
-0.3
0.9
0.35
3.6
V
V
Note 5-10
Note 5-12 This specification applies to all inputs and tri-stated bi-direct ional pins. Internal pull-down and pull-up
resistors add +/- 50uA per-pin (typical).
Note 5-13 XTAL1/CLKIN can optionally be driven from a 25MHz single-ended clock oscillator.
TABLE 5-4: VARIABLE I/O BUFFER CHARACTERISTICS
Parameter Symbol Min 1.8V
Typ 2.5V
Typ3.3V
Typ Max Units Notes
VIS Type Input Buffer
Low Input Level
High Input Level
Neg-Going Thresh old
Pos-Going Threshold
Schmitt Trigger Hyster-
esis (VIHT - VILT)
Input Leakage
(VIN = VSS or VDDIO)
Input Capacitance
VILI
VIHI
VILT
VIHT
VHYS
IIH
CIN
-0.3
0.64
0.81
102
-10
0.83
0.99
158
1.15
1.29
136
1.41
1.65
138
3.6
1.76
1.90
288
10
2
V
V
V
V
mV
uA
pF
Schmitt trigger
Schmitt trigger
Note 5-11
VO8 Type Buffers
Low Output Level
High Output Level
VOL
VOH VDDIO -
0.4
0.4 V
V
IOL = 8mA
IOH = -8mA
VOD8 Type Buffer
Low Output Level VOL 0.4 V IOL = 8mA
LAN8720A/LAN8720AI
DS00002165B-page 56 2016 Microchip Technology Inc.
Note 5-14 This specification applies to all inputs and tri-stated bi-direct ional pins. Internal pull-down and pull-up
resistors add +/- 50uA per-pin (typical).
TABLE 5-5: 100BASE-TX TRANSCEIVER CHARACTERISTICS
Parameter Symbol Min Typ Max Units Notes
Peak Differential Output Voltage High VPPH 950 —1050 mVpk Note 5-12
Peak Differential Output Voltage Low VPPL -950 —-1050 mVpk Note 5-12
Signal Amplitude Symmetry VSS 98 —102 %Note 5-12
Signal Rise and Fall Time TRF 3.0 —5.0 nS Note 5-12
Rise and Fall Symmetry TRFS — — 0.5 nS Note 5-12
Duty Cycle Distortion DCD 35 50 65 %Note 5-13
Overshoot and Undershoot VOS — — 5 % —
Jitter — — — 1.4 nS Note 5-14
Note 5-15 Measured at line side of transformer, line replaced by 100 (+/- 1%) resistor.
Note 5-16 Offset from 16nS pulse width at 50% of pulse peak.
2016 Microchip Technology Inc. DS00002165B-page 57
LAN8720A/LAN8720AI
Note 5-17 Measured differentially.
TABLE 5-6: 10BASE-T TRANSCEIVER CHARACTERISTICS
Parameter Symbol Min Typ Max Units Notes
Transmitter Peak D ifferential Outpu t Voltage VOUT 2.2 2.5 2.8 VNote 5-15
Receiver Differential Squelch Threshold VDS 300 420 585 mV —
Note 5-18 Min/max voltages guaranteed as measured with 100 resistive load.
5.5 AC Specifications
This section details the various AC timing specifications of the device.
Note 5-19 The SMI timing adheres to the IEEE 802.3 specification. Refer to the IEEE 802.3 specification for
additional timing information.
Note 5-20 The RMII timing adheres to the RMII Consortium RMII Specification R1.2.
5.5.1 EQUIVALENT TEST LOAD
Output timing specifications assume a 25pF equivalent test load, unless otherwise noted, as illustrated in Figure 5-1
below.
FIGURE 5-1: OUTPUT EQUIVALENT TEST LOAD
25 pF
OUTPUT
LAN8720A/LAN8720AI
DS00002165B-page 58 2016 Microchip Technology Inc.
5.5.2 POWER SEQUENCE TIMING
This diagram illustrates the device power sequencing requirements. The VDDIO, VDD1A, VDD2A and magnetics power
supplies can turn on in any order provided they all reach operational levels within the specified time period tpon. Device
power supplies can turn off in any order provided they all reach 0 volts within the specified time period poff.
FIGURE 5-2: POWER SEQUENCE TIMING
VDDIO
Magnetics
Power
tpon tpoff
VDD1A,
VDD2A
TABLE 5-7: POWER SEQU ENCE TIMING VALUES
Symbol Description Min Typ Max Units
tpon Power supply tu rn on time — — 50 mS
tpoff Power supply turn off time — — 500 mS
Note: When the intern al regulator is disabled, a po wer-up sequencing rela tionship exists between VDDCR and
the 3.3V power supply. For additional information refer to Section 3.7.4, REGOFF: Internal +1.2V Regula-
tor Configuration.
5.5.3 POWER-ON NRST & CONFIGURATION STRAP TIMING
This diagram illustrates the nRST reset and configuration strap timing requirements in relation to power-on. A hardware
reset (nRST assertion) is required fo llowing power-up. For proper op eration, nRST must be asserte d for no less than
trstia. The nRST pin can be asserted at any time, but must not be deasserted before tpurstd after all external power sup-
plies have reached 80% of their nominal operating levels. In order for valid configuration strap values to be read at
power-up, the tcss and tcsh timing constraints must be followed. Refer to Section 3.8.5, Re sets for additional information.
FIGURE 5-3: POWER-ON NRST & CONFIGURATION STRAP TIMING
tcss
nRST
Configuration Strap
Pins Input
trstia
tcsh
Configurati on Strap
Pins Output Drive
todad
All External
Power Supplies tpurstd
80%
tpurstv
totaa
TABLE 5-8: POWER-ON NRST & CONFIGURATION STRAP TIMING VALUES
symbol DESCRIPTION min typ max units
tpurstd External power supplies at 80% to nRST dea ssertion 25 — — mS
tpurstv External power supplies at 80% to nRST valid 0 — — nS
trstia nRST input assertion time 100 — — S
tcss Configuration strap pins setup to nRST deassertion 200 — — nS
tcsh Configuration strap pins hold after nRST deassertion 1 — — nS
totaa Outpu t tri-state after nR ST assertion —50 nS
todad Output drive after nRST deassertion 2 — 800
(Note 5-
20)
nS
2016 Microchip Technology Inc. DS00002165B-page 59
LAN8720A/LAN8720AI
Note 5-21 nRST deassertion must be monotonic.
Note 5-22 Device configuration straps are latched as a result of nRST assertion. Refer to Section 3.7,
Configuration Straps for details. Configuration straps must only be pulled high or low and must not
be driven as inputs.
Note 5-23 20 clock cycles for 25MHz, or 40 clock cycles for 50MHz.
LAN8720A/LAN8720AI
DS00002165B-page 60 2016 Microchip Technology Inc.
5.5.4 RMII INTERFACE TIMING
5.5.4.1 RMII Timing (REF_CLK Out Mode)
The 50MHz REF_C LK OUT timing applies to the case when nINTSEL is pul led-low. In this mode, a 25MHz crystal or
clock oscillator must be input on the XT AL1/CLKIN and XTAL2 pins. For more information on REF_CLK Out Mode, see
Section 3.7.4.2, REF_CLK Out Mode.
FIGURE 5-4: RMII TIMING (REF_CLK OUT MODE)
REFCLKO
RXD[1:0],
RXER
CRS_DV
tclkh tclkl
tclkp
toval tohold
toval
toval
tohold
tsu
TXD[1:0]
TXEN
tihold tsu tihold tihold
tsu
tihold
TABLE 5-9: RMII T IMING VALUES (REF_CLK OUT MODE)
Symbol Description Min Max Units Notes
tclkp REFCLKO period 20 —ns —
tclkh REFCLKO high time tclkp*0.4 tclkp*0.6 ns —
tclkl REFCLKO low time tclkp*0.4 tclkp*0.6 ns —
toval RXD[1:0], RXER, CRS_DV output valid from ris-
ing edge of REFCLKO —5.0 ns Note 5-24
tohold RXD[1:0], RXER, CRS_DV output hold from ris-
ing edge of REFCLKO 1.4 —ns Note 5-24
tsu TXD[1:0], TXEN setup time to rising edge of
REFCLKO 7.0 —ns Note 5-24
tihold TXD[1:0], TXEN input hold time after rising edge
of REFCLKO 2.0 —ns Note 5-24
Note 5-24 Timing was designed for system load between 10 pf and 25 pf.
2016 Microchip Technology Inc. DS00002165B-page 61
LAN8720A/LAN8720AI
5.5.4.2 RMII Timing (RE F_C L K In Mo de )
The 50MHz REF_CLK IN timing applies to the case when nINTSEL is floate d or pulled-high. In this mod e, a 50MHz
clock must be input on the CLKIN pi n. For more informa tion on REF_CL K In Mode, see Section 3.7.4.1, REF_ CLK In
Mode.
FIGURE 5-5: RMII TIMING (REF_CLK IN MODE)
CLKIN
(REF_CLK)
RXD[1:0],
RXER
CRS_DV
tclkh tclkl
tclkp
toval tohold
toval
toval
tohold
tsu
TXD[1:0]
TXEN
tihold tsu tihold tihold
tsu
tihold
TABLE 5-10: RMII TIMING VALUES (REF_CLK IN MODE)
Symbol Description Min Max Units Notes
tclkp CLKIN period 20 —ns —
tclkh CLKIN high time tclkp*0.35 tclkp*0.65 ns —
tclkl CLKIN low time tclkp*0.35 tclkp*0.65 ns —
toval RXD[1:0], RXER, CRS_DV output valid from ris-
ing edge of CLKIN —14.0 ns Note 5- 25
tohold RXD[1:0], RXER, CRS_DV output hold from ris-
ing edge of CLKIN 3.0 —ns Note 5-25
tsu TXD[1:0], TXEN setup time to rising edge of
CLKIN 4.0 —ns Note 5-25
tihold TXD[1:0], TXEN input hold time after rising edge
of CLKIN 1.5 —ns Note 5-25
Note 5-25 Timing was designed for system load between 10 pf and 25 pf.
LAN8720A/LAN8720AI
DS00002165B-page 62 2016 Microchip Technology Inc.
5.5.4.3 RM II CL KIN Re qu irem en ts
TABLE 5-11: RMII CLKIN (REF_CLK) TIMING VALUES
Parameter Min Typ Max Units Notes
CLKIN frequency 50 —MHz —
CLKIN Frequency Drift —± 50 ppm —
CLKIN Duty Cycle 40 —60 % —
CLKIN Jitter —150 psec p-p – not RMS
5.5.5 SMI TIMING
This section specifies the SMI timing of the device. Please refer to Section 3.5, Serial Management Interface (SMI) for
additional details.
FIGURE 5-6: SMI TIMING
MDC
MDIO
tclkh tclkl
tclkp
tohold
MDIO
tsu tihold
(Data-Out)
(Data-In)
tohold
tval
TABLE 5-12: SMI TIMING VALUES
Symbol Description Min Max Units Notes
tclkp MDC period 400 —ns —
tclkh MDC high time 160 (80%) —ns —
tclkl MDC low time 160 (80%) —ns —
tval MDIO (read from PHY) output valid from rising
edge of MDC —300 ns —
tohold MDIO (read from PHY) output hold from rising
edge of MDC 0 — ns —
tsu MDIO (write to PHY) setup time to rising edge of
MDC 10 —ns —
tihold MDIO (write to PHY) input hold time after rising
edge of MDC 10 —ns —
2016 Microchip Technology Inc. DS00002165B-page 63
LAN8720A/LAN8720AI
5.6 Clock Circuit
The device can accept ei ther a 25MHz crystal (preferre d) or a 25MHz single-end ed clock oscillator (±50ppm) in put. If
the single-ended clock oscillator method is implemented, XTAL2 should be left unconnected and XTAL1/CLKIN should
be driven with a nominal 0-3.3V clock signal.
It is recommended th at a crystal utilizing matching parallel load capacitors be used for the crystal input/out put signals
(XT AL1/XTAL2). Either a 300uW or 100uW 25MHz crystal may be utilized. The 300uW 25MHz crystal specifications are
detailed in Section 5. 6.1, "300 uW 25 MH z Crystal Specificati on, " on page 65. The 100uW 25MHz crystal specifi ca ti ons
are detailed in Section 5.6.2, "100uW 25MHz Crystal Specification," on page 66.
5.6.1 300UW 25MHZ CRYSTAL SPECIFICATION
When utilizing a 300uW 25MHz crystal, the following circuit design (Figure 5-8) and specifications (Table 5-12) are
required to ensure proper operation.
FIGURE 5-7: 300UW 25MHZ CRYSTAL CIRCUIT
LAN8720
XTAL2
XTAL1
Y1
C1C2
TABLE 5-13: 300UW 25MHZ CRYSTAL SPECIFICATIONS
Parameter Symbol Min Nom Max Units Notes
Crystal Cut AT, typ —
Crystal Oscillation Mode Fundamental Mode —
Crystal Calibration Mode Parallel Resonant Mode —
Frequency Ffund —25.000 —MHz —
Frequency Tolerance @ 25oC Ftol — — ±50 PPM Note 5-26
Frequency Stability Over Temp Ftemp — — ±50 PPM Note 5-26
Frequency Deviation Over Time Fage —+/-3 to 5 —PPM Note 5-27
Total Allowable PPM Budget — — — ±50 PPM Note 5-28
Shunt Capacitance CO—7 typ —pF —
Load Capacitance CL—20 typ —pF —
Drive Level PW300 — — uW —
Equivalent Series Resistance R1— — 30 Ohm —
Operating Temperature Range —Note 5-35 —+85 oC —
XTAL1/CLKIN Pin Capacitance — — 3 typ —pF Note 5-30
XTAL2 Pin Capacitanc e — — 3 typ —pF Note 5-30
LAN8720A/LAN8720AI
DS00002165B-page 64 2016 Microchip Technology Inc.
Note 5-26 The maximum allowable values for Frequency Tolerance and Frequency Stability are application
dependent. Since any particular application must meet the IEEE ±50 PPM Total PPM Budget, the
combination of these two values must be approximately ±45 PPM (allowing for aging).
Note 5-27 Frequency Deviation Over Time is also referred to as Aging.
Note 5-28 The total deviation for the Transmitter Clock Frequency is specified by IEEE 802.3u as
±100 PPM.
Note 5-29 0oC for extended commercial version, -40oC for industrial version.
Note 5-30 This number includes the pad, the bond wire and the lead frame. PCB capacitance is not included
in this value. The XTAL1/CLKIN pin, XTAL2 pin and PCB capacitance values are required to
accurately calculate the value of the two external load capacitors. The total load capacitance must
be equivalent t o what the crystal expects to see in th e circuit so that the crystal oscillator will op erate
at 25.000 MHz.
5.6.2 100UW 25MHZ CRYSTAL SPECIFICATION
When utilizing a 100uW 25MHz crystal, the following circuit design (Figure 5-9) and specifications (Table 5-13) are
required to ensure proper operation.
FIGURE 5-8: 100UW 25MHZ CRYSTAL CIRCUIT
LAN8720
XTAL2
XTAL1
RSY1
C1C2
TABLE 5-14: 100UW 25MHZ CRYSTAL SPECIFICATIONS
Parameter Symbol Min Nom Max Units Notes
Crystal Cut AT, typ —
Crystal Oscillation Mode Fundamental Mode —
Crystal Calibration Mode Parallel Resonant Mode —
Frequency Ffund —25.000 —MHz —
Frequency Tolerance @ 25oC Ftol — — ±50 PPM Note 5-31
Frequency Stability Over Temp Ftemp — — ±50 PPM Note 5-31
Frequency Deviation Over Time Fage —±3 to 5 —PPM Note 5-32
Total Allowable PPM Budget — — — ±50 PPM Note 5-33
Shunt Capacitance CO— — 5 pF —
Load Capacitance CL8 — 12 pF —
Drive Level PW—100 —uW Note 5-34
2016 Microchip Technology Inc. DS00002165B-page 65
LAN8720A/LAN8720AI
Note 5-31 The maximum allowable values for Frequency Tolerance and Frequency Stability are application
dependent. Since any particular application must meet the IEEE ±50 PPM Total PPM Budget, the
combination of these two values must be approximately ±45 PPM (allowing for aging).
Note 5-32 Frequency Deviation Over Time is also referred to as Aging.
Note 5-33 The total deviation for the Transmitter Clock Frequency is specified by IEEE 802.3u as
±100 PPM.
Note 5-34 The crystal must support 100uW operation to utilize this circuit.
Note 5-35 0oC for extended commercial version, -40oC for industrial version.
Note 5-36 This number includes the pad, the bond wire and the lead frame. PCB capacitance is not included
in this value. The XTAL1/CLKIN pin, XTAL2 pin and PCB capacitance values are required to
accurately calculate the value of the two external load capacitors. The total load capacitance must
be equivalent t o what the crystal expects to see in th e circuit so that the crystal oscillator will op erate
at 25.000 MHz.
Equivalent Series Resistance R1— — 80 Ohm —
XTAL2 Series Resistor Rs495 500 505 Ohm —
Operating Temperature Range —Note 5-35 —+85 oC —
XTAL1/CLKIN Pin Capacitance — — 3 typ —pF Note 5-36
XTAL2 Pin Capacitanc e — — 3 typ —pF Note 5-36
TABLE 5-14: 100UW 25MHZ CRYSTAL SPECIFICATIONS (CONTINUED)
Parameter Symbol Min Nom Max Units Notes
LAN8720A/LAN8720AI
DS00002165B-page 66 2016 Microchip Technology Inc.
6.0 PACKAGE INFORMATION
6.1 24-QFN (Punch)
Min Nominal Max Remarks
A0.70 0.85 1.00 Overall Package Height
A1 00.02 0.05 Standoff
A2 — — 0.90 Mold Cap Thickness
D/E 3.90 4.00 4.10 X/Y Body Size
D1/E1 3.55 3.75 3.95 X/Y Mold Cap Size
D2/E2 2.40 2.50 2.60 X/Y Exposed Pad Size
L0.30 0.40 0.50 Terminal Length
b0.18 0.25 0.30 Terminal Width
k0.25 — — Terminal to Exposed Pad Clearance
e0.50 BSC Terminal Pitch
Note 1: All dimensions are in millimeters unles s otherwise noted.
2: Dimension “b” applies to plated terminals and is measured between 0.15 and 0.30 mm from the terminal tip.
3: The pin 1 identifier may vary, but is always located within the zone indicated.
2016 Microchip Technology Inc. DS00002165B-page 67
LAN8720A/LAN8720AI
LAN8720A/LAN8720AI
DS00002165B-page 68 2016 Microchip Technology Inc.
6.2 24-SQFN (Sawn)
2016 Microchip Technology Inc. DS00002165B-page 69
LAN8720A/LAN8720AI
6.3 Tape & Reel Information
Note: Standard reel size is 5,000 pieces per reel.
LAN8720A/LAN8720AI
DS00002165B-page 70 2016 Microchip Technology Inc.
2016 Microchip Technology Inc. DS00002165B-page 71
LAN8720A/LAN8720AI
7.0 APPLICATION NOTES
7.1 Application Diagram
The device requires few external components. The voltage on the magnetics center tap can range from 2.5 - 3.3V.
7.1.1 RMII DIAGRAM
FIGURE 7-1: SIMPLIFIED APPLICATION DIAGRAM
LAN8720
10/100 PH Y
24-QFN
RMII
TXP
TXN
Mag RJ45
RXP
RXN
25MHz
XTAL1/CLKIN
XTAL2
TXD[1:0]
2
RXD[1:0]
RXER
2
RMII
LED[2:1]
2
Interface
MDIO
MDC
nINT
nRST
TXEN
7.1.2 POWER SUPPLY DIAGRAM
FIGURE 7-3: HIGH-LEVEL SYSTEM DIAGRAM FOR POWER
LAN8720
24-QFN
RBIAS 24
VSS
19
12k
VDD1A
nRST
15
CBYPASS
1
CBYPASS
VDD2A
VDDIO
CBYPASS
CF
VDDDIO
Supply
1.8 - 3.3V
Analog
Supply
3.3V
C
9
Power to
magnetics
interface.
R
VDDCR
6
1uF
LAN8720A/LAN8720AI
DS00002165B-page 72 2016 Microchip Technology Inc.
7.1.3 TWISTED-PAIR INTERFACE DIAGRAM
FIGURE 7-5: COPPER INTERFACE DIAGRAM
Magnetics
LAN8720
24-QFN
1
VDD2A CBYPASS
21
TXP
TXN
Analog
Supply
3.3V
1
2
3
4
5
6
7
8
20
1000 pF
3 kV
RJ45
75
75
23
RXP
RXN 22
CBYPASS
19
VDD1A CBYPASS
49.9 Resistors Magnetic
Supply
2.5 - 3.3V
2016 Microchip Technology Inc. DS00002165B-page 73
LAN8720A/LAN8720AI
APPENDIX A: DATA SHEET REVISION HISTORY
TABLE A-1: REVISION HISTORY
Revision Section/Figure/Entry Correction
Rev B. (07-15-16) Section 5.1, "Absolute Maxi-
mum Ratings*," on page 54 Update to Positive voltage on XTAL1/CLKIN, with
respect to ground.
Table 5-2, “Non-Variable I/O
Buffer Characteristics,” on
page 56
Update to min/max values for the last row, ICLK
Type Buffer (XTAL1 Input) - High Input Level.
Rev. A (06-24-16) All Document converted to Microchip look and feel.
Replaces SMSC Rev. 1.4 (08-23-12).
Section 5.2, "Operating Con-
ditions**," on page 54 Increased VDDCR operational limits from “+1.14V
to +1.26V” to “+1.08V to +1.32V”
Section 5.6, "Clock Circuit, "
on page 65 Added new 100uW crystal specifications and circuit
diagram. The section is now split into two subsec-
tions, one for 300uW crystals and the other for
100uW crystals.
Section 6.0, "Package Infor-
mation," on page 68 Added new subsectio ns to include SQFN package
information.
Section , "Produ ct Id en tif ica -
tion System," on page 77 Updated ordering codes with sawn SQFN package
options.
Rev. 1.4
(08-23-12) Section 4.2.2, Basic Status
Register Updated definitions of bits 10:8.
Rev. 1.3
(04-20-11) Table 5-9, “RMII Timing Val-
ues (REF_CLK Out Mode),”
on page 60
Updated toval maximum value from 10.0ns to 5.0ns.
Rev. 1.2 (11-10-10) Section 5.5.5, "RMII Inter-
face Timing," on page 63 Updated diagrams and tables to include RXER.
LAN8720A/LAN8720AI
DS00002165B-page 74 2016 Microchip Technology Inc.
THE MICROCHIP WEB SITE
Microchip provides online support via our WWW site at www.microchip.com. This web site is used as a means to make
files and information easily available to customers. Accessible by using your favorite Internet browser , the web site con-
tains the following information:
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guides and hardware support documents, latest software releases and archived software
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CUSTOMER CHANGE NOTIFICATION SERVICE
Microchip’s customer notification service help s keep customers current on Microchip products. Subscribers will receive
e-mail notification whenever there are changes, updates, revisions or errata related to a specified product family or
development tool of interest.
To register, access the Mi cro chip web site at www.microchip.com. Under “Support”, click on “Cust omer Ch ange Not if i -
cation” and follow the registration instructions.
CUSTOMER SUPPORT
Users of Microchip products can receive assistance through several channels:
• Distributor or Representative
• Local Sales Office
• Field Application Engineer (FAE)
• Technical Support
Customers should contact their distributor, representative or field application engineer (FAE) for support. Local sales
offices are also available to help customers. A listing of sales offices and locations is included in the back of this docu-
ment.
Technical support is available through the web site at: http://microchip.com/support
2016 Microchip Technology Inc. DS00002165B-page 75
LAN8720A/LAN8720AI
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
Device: LAN8720A
Temperature
Range: CP = 0C to +85C (Extended Commercial)
i-CP = -40C to +85C (Industrial)
Tape and Reel
Option: Blank = Standard packaging (tray)
TR = Tape and Reel(1)
Package: Blank = Punch Package (24-QFN)
ABC = Sawn Package (24-SQFN)
Examples:
a) LAN8720Ai-CP-TR
Industrial temp., Tape & Reel, 24-QFN (Punch)
b) LAN8720A-CP-ABC
Ext. commer cia l te m p ., Tray, 24-SQFN (Sawn)
Note 1: Tape and Reel identifier only appears in the
catalog part number description. This
identifier is used for ordering purposes and is
not printed on the device package. Check
with your Microchip Sales Office for package
availability wit h the Tape and Reel option.
PART NO. [X]
Temperature
Range
Device
[X](1)
Tape & Reel
Option
--[XXX]
Package
LAN8720A/LAN8720AI
DS00002165B-page 76 2016 Microchip Technology Inc.
NOTES:
2016 Microchip Technology Inc. DS00002165B-page 77
LAN8720A/LAN8720AI
Information contained in this publication regarding device applications and the like is provided only for your convenience and may be
superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO
REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELA TED TO THE INFORMA TION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE,
MERCHANT ABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Micro-
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harmless Microchip from any and all damages, claims, suits, or expe nses resulting from such use. No licenses are conveyed, implicitly or
otherwise, under any Microchip intellectual property rights unless otherwise state d.
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Analog-for-the-Digital Age, Any Capacitor , AnyIn, AnyOut, BodyCom, chipKIT, chipKIT logo, CodeGuard, dsPICDEM, dsPICDEM.net,
Dynamic Average Matching, DAM, ECAN, EtherGREEN, In-Circuit Serial Programming, ICSP, Inter-Chip Connectivity, JitterBlocker,
KleerNet, KleerNet logo, MiWi, motorBench, MPASM, MPF, MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach,
Omniscient Code Generation, PICDEM, PICDEM.net, PICkit, PICtail, PureSilicon, RightTouch logo, REAL ICE, Ripple Blocker, Serial
Quad I/O, SQI, SuperSwitcher, SuperSwitcher II, Total Endurance, TSHARC, USBCheck, VariSense, ViewS p an, WiperLock, Wireless
DNA, and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated in the U.S.A.
Silicon Storage Technology is a registered trademark of Microchip Technology Inc. in other countries.
GestIC is a registered trademarks of Microchip Technology Germany II GmbH & Co. KG, a subsidiary of Microchip Technology Inc., in
other countries.
All other trademarks mentioned herein are property of their respective companies.
© 2016, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved.
ISBN: 978-1-5224-0780-5
Note the following details of the code protection feature on Microchip devices:
• Microchip products meet the specification contained in their particular Microchip Data Sheet.
• Microchip believes that it s family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Dat a
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
• Microchip is willing to work with the customer who is concerned about the integrity of their code.
• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection featur es of our
products. Attempts to break Microchip’ s code protection feature may be a violation of the Digit al Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Microchip received ISO/TS-16949:200 9 certif ication for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperi pherals, nonvola tile memo ry and
analog product s. In addition, Microchip ’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
QUALITYMANAGEMENTS
YSTEM
CERTIFIEDBYDNV
== ISO/TS16949==
DS00002165B-page 78 2016 Microchip Technology Inc.
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Worldwide Sales and Service
06/23/16
