SI3453D-B02-GMR - Silicon Labs

This information applies to a product under development. Its characteristics and specifications are subject to change without notice.

QUAD HIGH-VOLTAGE PORT CONTROLLER FOR POE AND POE+ PSES

Features

Applications

Each Si3452/3 High Voltage Port

Controller supports four PSE power

interfaces

Programmable current limits for PoE

(15.4 W), PoE+ (30 W), and

proprietary systems (up to 40 W) per

port

I2C interface requires no external

MCU for easy, low-cost management

of 4 to 48 ports by the host system.

Unique high-voltage component

integration simplifies design, lowers

power dissipation, minimizes

external BOM, and reduces PCB

footprint

Internal low-RON power FETs with

current sense circuitry

Integrated transient voltage surge-

suppressors

DC disconnect (Si3453) or

proprietary dV/dt™ disconnect

(Si3452) sensing methods

Programmable architecture supports

IEEE 802.3af (PoE) and pre-

standard IEEE 802.3at (PoE+) PSEs

Programmable current limits for

PoE (350 mA) and PoE+

(600 mA), and custom limits to

850 mA

Per-port current and voltage

monitoring for sophisticated power

management and control

Power policing mode

Robust multi-point detection

Supports 1-Event and 2-Event

classification algorithms

Comprehensive, robust fault

protection circuitry

Supply under voltage lockout

(UVLO)

Output current limit and short

circuit protection

Foldback current limiting

Dual-threshold thermal overload

protection

Fault source reporting for

intelligent port management

Extended operating temperature

range: –10 to 85 ºC

Compact, 6×6 mm2, 40-pin QFN

package. RoHS-compliant

Power over Ethernet Endpoint

switches and Midspans for IEEE Std

802.3af and 802.3at

Supports high power PDs, such as:

Pan/Tilt/Zoom security cameras

802.11n WAPs

Multi-band, multi-radio WAPs

Security and RFID systems

Industrial automation systems

Networked audio

IP Phone Systems and iPBXs

Metropolitan area networked WAPs,

cameras, and sensors

WiMAX ASN/BTS and CPE/ODU

systems

Ordering Information:

See page 29.

Pin Assignments

40-pin QFN

See "8. Pin Descriptions" on page 26.

VEE

VEE1

AIN

RBIAS

VREF

AGND

AOUT

AGND 8

DGND

VDD

AD1

AD3

AD0

AD2

VOUT4

SDA

DET4

SCL

GND34

DET3 18

VDD 19

VOUT1

INT

DET1

AD0

RST

GND12

AD1

DET2

VEE4 10

NC 9VEE3

RST

AD3

VOUT3 20

32 VOUT2

31 VEE2

Si3452

(Top View)

Si3452/3

2 Rev. 0.42

Description

When connected directly to the host system or configured in Auto mode, each Si3452/3 high voltage port controller

provides all of the critical circuitry and sophisticated power measurement functionality for the high voltage

interfaces of four complete PSE ports. The Si3452/3 fully integrates robust, low-RON (0.3  typ.) power MOSFET

switches; low power dissipation current sensing circuitry; and transient voltage surge-suppression devices.

The on-chip current sense circuitry and power MOSFETs provide programmable scaling of current limits to match

either PoE (350 mA, 15.4 W), PoE+ (600 mA, 30 W) and extended (800 mA, 40 W) power requirements on a per-

port basis. Designed for use in Endpoint PSE (e.g., Ethernet switches) or Midspan PSE (e.g., inline power

injectors) applications, each Si3452/3 also performs the IEEE-required powered device (PD) detection,

classification, and disconnect functionality.

The flexible architecture enables powered device disconnect detection using either DC disconnect (Si3453), or

Silicon Laboratories' proprietary dV/dt™ disconnect (Si3452) sensing algorithm. dV/dt disconnect is an alternative

to DC disconnect that requires no additional BOM components, does not dissipate extra device power, and fully

interoperates with all powered devices. Also provided are multi-point detection algorithms, and per-port current and

voltage monitoring.

Intelligent protection circuitry includes power supply under voltage lockout (UVLO); port output current limiting and

short circuit protection; thermal overload sensing and port shutdown; and transient voltage surge-suppressors

capable of protecting the Si3452/3 from a variety of harsh surge events seen on the RJ-45 interface.

To maximize system design flexibility and minimize cost, each Si3452/3 connects directly to a system host

controller through an I2C serial interface, eliminating the need for an external MCU. The Si3452/3 can be set to one

of 12 unique addresses, allowing control of up to 48 ports on a single I2C bus.

Functional Block Diagram

PER PORT ANALOG

AD2

AD1

AD3

HV SPI

Port

Control

VEE1

VOUT1

AOUT

Gate Control,

Current Limit

& Foldback

Detection

Classification

DC or

dV/dt™

Disconnect

Channel

Mode

Limit

Control

VREF & Central Bias

MEAS.

MUX

PGA

DET4

VOUT2

VOUT3

DET3

DET2

GND12

AGND

VDD

VEE3

Thermal

Prot.

RBIAS

AD0

VEE2

VEE4

DET1

VOUT4

Current

Sense

VREF

VEE

DGND

AMUX

10b

ADC

Temp

Sensor

AIN

LV SPI

AD1

AD0

AD2

AD3

MCU Core

& PSE FSM

256 Byte SRAM

8 kByte EPROM

I2C

RST

PLL

Voltage

Regulator

& Monitor

VDD

AGND

POR

WDT

INT

GND34

RST

SDA

SCL

Si3452/3

Rev. 0.42 3

TABLE OF CONTENTS

Section Page

1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. PSE System-Level Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

3. PSE Application Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

4. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

4.1. Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

4.2. Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

4.3. Port Turn-on and Power FETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

4.4. Disconnect Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4.5. Transient Voltage Surge Suppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4.6. Temperature Sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4.7. Port Measurement and Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

4.8. SMBus/I2C Interface Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

5. Register Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

5.1. Interrupt (Registers 0x00–0x01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

5.2. Port Event (Registers 0x02–0x05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

5.3. Port Status (Registers 0x06–0x09) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

5.4. Port Configuration (Registers 0x0A–0x011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

5.5. Command and Return Registers (Registers 0x12–0x1C) . . . . . . . . . . . . . . . . . . . . .19

5.6. Device Status Register (0x1D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

6. Operational Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

6.1. Port Turn On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

6.2. Changing the Interrupt Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

7. PCB Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

8. Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

9. Package Outline: 40-Pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

10. Recommended PCB Footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

11. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

11.1. Evaluation Kits and Reference Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

12. Device Marking Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Si3452/3

4 Rev. 0.42

1. Electrical Specifications

Unless noted otherwise, specifications apply over the operating temperature range with VDD = +3.3 V, and

VEE = –48 V relative to GND.

VDD pins should be electrically shorted. AGND pins, DGND, GND12, and GND34 should be electrically shorted

("GND"). VEE, VEE1, VEE2, VEE3, and VEE4 should be electrically shorted ("VEE").

VPort for any port is measured from GND to the respective VOUTn.

Table 1. Absolute Maximum Ratings1

Type Description Rating Unit

Supply voltages VEE to GND –62 to +0.3 V

VDD to GND –0.3 to +3.6 V

VDD1 to VDD2 –0.3 to +0.3 V

Any VEE to any other VEE –0.3 to +0.3 V

Any GND to any other GND –0.3 to +0.3 V

Voltage on digital pins SDA, SCL, ADn, RST, INT (GND – 0.3) to (VDD + 0.3) V

Voltage on analog pins VREF, AIN, AOUT, RBIAS, OSC (GND – 0.3) to (VDD + 0.3) V

VOUTn, DETn (VEE – 0.3) to (GND + 0.3) V

DETn peak currents during surge events2±5 A

Maximum continuous power dissipation31.2 W

Maximum junction temperature 125 °C

Ambient storage temperature –55 to 150 °C

Lead temperature (soldering, 10 seconds maximum) 260 °C

Notes:

1. Functional operation should be restricted to those conditions specified in the Recommended Operating Conditions

section of this data sheet. Functional operation or specification compliance is not implied at these conditions. Stresses

beyond those listed in Absolute Maximum Ratings may cause permanent damage to the device.

2. See IEEE Std 802.3-2005, clause 33.4 for a description of surge events.

3. If all ports are on with 600 mA load, the power dissipation is <1.2 W. At 85 °C ambient with the expected 32 °C/W

thermal impedance, the junction temperature would be 123.4 °C, which is within the 125 °C maximum rating.

Si3452/3

Rev. 0.42 5

Table 2. Recommended Operating Conditions

Description Symbol Test Conditions Min Typ Max Unit

Operating temperature TA–10 — 85 °C

Thermal impedance*

θJA

No airflow — 32 —

°C/W

1 m/s airflow — 28 —

Power Supply Voltages

VEE supply voltage

VEE

For IEEE 802.3af (15.4 W) apps. –57 –48 –45 V

For IEEE 802.3at (30 W) apps. –57 –54 –51

VDD supply voltage VDD 3.0 3.3 3.6 V

Power Supply Currents

VEE supply current

IEE

All ports on, excluding load current. — 4 —

All ports in shutdown mode — 1 5

VDD supply current IDD —10—mA

*Note: Modeled with six parts, evenly spaced on a 30 x 120 mm2, four-layer board with 25 thermal vias to a Vneg plane on

the back.

Table 3. UVLO, and Reset Specifications

Description Symbol Test Conditions Min Typ Max Unit

VDD reset threshold VRST —1.75 — V

VDD power-on ramp*Ramp from 0 V to 1.8 V — — 1 ms

RST input high voltage 0.7 x VDD —— V

RST input low voltage — — 0.8 V

RST input leakage RST =0V — — 40 μA

Reset time delay TRSTDLY

Time between end of reset and begin-

ning of normal operation — — TBD msec

Reset assertion time TRST

RST low time to generate system

reset 15 — — μs

VEE monitor accuracy VEEMON

Measured VEE relative to actual VEE

for VEE (–44 to –57 V) –1.5 — 1.5 V

VEE UVLO threshold

VUVLO

Point at which VEE UVLO is declared.

VEE going negative

VEE going positive

—

–36

–33

—

*Note: If VDD ramp time is slower than 1 msec, hold the reset pins low until VDD is above 3.0 V to insure proper

reset operation.

Si3452/3

6 Rev. 0.42

Table 4. Detection Specifications

Description Symbol Test Conditions Min Typ Max Unit

Detection current limit ILIM_DET Measured with DETn

shorted to GND

—3 5mA

Detection voltage,

when RDET =25kΩ

VDET1

VDET2

VDET3

—

–4.0

–8.0

–4.0

—

Detection slew rate — — 0.1 V/μs

Detection probe duration TPROBE 10 — 30 ms

Detection probe cycle time TDET ——500ms

Minimum valid signature resistance RDET_MIN 15 — 19 k

Maximum valid signature resistance RDET_MAX 26.5 — 33 k

Resistance at which open circuit is declared ROPEN 100 — 400 k

Resistance at which short circuit is declared RSHORT 150 — 400 

Valid detect capacitance CDET_VALID ——150nF

Invalid detect capacitance CDET_INVALD 10 — — μF

Si3452/3

Rev. 0.42 7

Table 5. Classification Specifications

Description Symbol Test Conditions Min Typ Max Unit

Class event voltage VCLASS 0mA < I

Port < 45 mA –15.5 — –20.5 V

Mark event voltage VMARK 0mA < I

Port < 5 mA –7 — –10 V

Classification current

limit

ILIM_CLASS Measured with DETn shorted to

GND

55 — 100 mA

Classification current

regions

Class 0

Class 1

Class 2

Class 3

Class 4

Overcurrent

—

Classification delay TCLASS_DLY Time from end of valid detect cycle

to classification begin

—5—ms

Classification event time TCLE Width of valid VCLASS probe for 1-

Event or 2-Event classification

10 — 30 ms

Mark event time TME Width of mark between classification

events

—8—ms

Table 6. VOUT Drive and Power-on Specifications

Description Symbol Test Conditions Min Typ Max Unit

Max output resistance

(port on)

RON IPort ≤ 720 mA — 0.3 0.6 Ω

VOUTn operating

current limit

ILIM PoE (<15.4 W) mode

PoE+ (>15.4 W) mode

400

800

425

850

450

—

Overload current

threshold

ICUT Class 0

Class 1 (class policing enabled)1

Class 2 (class policing enabled)1

Class 3

Class 42

350

160

350

600

—

Over current time limit3TOVLD Load current ≥ ICUT or ILIM 50 — 75 ms

VOUTn turn-on slew TRISE 10% to 90% 15 70 — µs

Power turn on timing TPON Time from end of valid detect to

power on

——400ms

VOUTn leakage current IOUT_LEAK Port in shutdown — 10 — µA

Notes:

1. In auto mode, class policing is automatically enabled. In manual mode, ICUT must be programmed manually.

See "5.4. Port Configuration (Registers 0x0A–0x011)" on page 18 for more information.

2. 600 mA is consistent with the IEEE 802.3at draft standard. ICUT is user-programmable in 3.2 mA

increments to over 800 mA for non-standard applications.

3. For 2x mode and extreme overload or short-circuit events, TOVLD will dynamically decrease to prevent

excessive FET heating. This is consistent with the 802.3at draft.

Si3452/3

8 Rev. 0.42

Table 7. DC- and dV/dt™ Disconnect Specifications

Description Symbol Test Conditions Min Typ Max Unit

Load current to prevent

disconnect

ION 10 — — mA

Load current to

guarantee disconnect

IOFF dc disconnect — — 5 mA

dV/dt™ disconnect — — 2 mA

Disconnect delay TDCDV_DLY Time from IOFF load current to port

turn off

300 — 400 ms

Table 8. Port Measurement and Monitoring Specifications

Description Symbol Test Conditions Min Typ Max Unit

Port current measurement

offset IOFFSET 0 ≤ IPORT ≤ ICUT

. For final IPORT

reading, add offset to % of reading

tolerance.

–2 — 2 mA

Port current measurement

tolerance %TOL –4 — 4 %

Table 9. SMBus (I2C) Electrical Specifications

Description Symbol Test Conditions Min Typ Max Unit

Input low voltage VIL

SCL, SDA pins @ –10 °C — — 0.9 V

SCL, SDA pins @ full temp range 0.8

Input high voltage VIH SCL, SDA pins 0.7 ×

VDD

—— V

Output low voltage VOL SCL, SDA pins,

driving ≤ 8.5 mA

——0.6V

Input leakage current ILSCL, SDA pins — — 40 µA

Table 10. Address Pin Electrical Specifications*

Description Symbol Test Conditions Min Typ Max Unit

Input low voltage VIL AD0, AD1, AD2, AD3 pins 0.8 V

Input high voltage VIH AD0, AD1, AD2, AD3 pins 0.7 x

VDD

—— V

Input leakage current IH, ILAD0, AD1, AD2, AD3 pins –10 — 10 µA

*Note: At power-up, these pins are logic inputs. A 10 k pull up or pull down resistor is used for address selection. After

address recognition, the pins are used for internal communications.

Si3452/3

Rev. 0.42 9

Figure 1. I2C Timing Diagram

Table 11. SMBus (I2C) Timing Specifications (see Figure 1)

Description Symbol Test Conditions Min Typ Max Unit

Serial bus clock frequency fSCL 0—400kHz

SCL high time tSKH 600 — — ns

SCL low time tSKL 1.3 — — μs

SCL, SDA rise time tR_SCL 20 — 300 ns

SCL, SDA fall time tF_SCL 20 — 150 ns

Bus free time tBUF Between START and STOP

conditions.

1.3 — — μs

Start hold time tSTH Between START and first low SCL. 600 — — ns

Start setup time tSTS Between SCL high and START

condition.

600 — — ns

Stop setup time tSPS Between SCL high and STOP

condition.

600 — — ns

Data hold time tDH 150 — — ns

Data setup time tDS 200 — — ns

Time from hardware or soft-

ware reset until start of I2C

traffic.

tRESET Reset to start condition TBD — — ms

Notes:

1. Not production tested (guaranteed by design).

2. All timing references measured at VIL and VIH.

3. The Si3452/3 will stretch (pull down on) SCK during the ACK time period if required. The maximum SCL stretching is

10 µsec; so, SCL only needs to be bidirectional for I2C bus speeds over 50 kHz.

SCL

fSC L tR_SCL tF_SC L tSK H

SDA

tSKL

tST H tSPS

D6 D5 D4 D3 D0

tDS tDH

Star t Bit Stop Bit

tBUF

Si3452/3

10 Rev. 0.42

Table 12. Interrupt (INT) Specifications

Description Symbol Test Conditions Min Typ Max Unit

Output low voltage VOL INT pin driving ≤ 8.5 mA — — 0.6 V

Table 13. Input Voltage Reference Specifications

Description Symbol Test Conditions Min Typ Max Unit

Nominal VREF input — 1.1 — V

Reference tolerance — 1 TBD %

VREF loading Input current — — TBD µA

Si3452/3

Rev. 0.42 11

2. PSE System-Level Diagrams

Figure 2. 4-Port System with Direct Host Connection

3. PSE Application Diagrams

Figure 3. 4-Port Application Diagram Using DC– or dV/dt Disconnect and I2C Host Interface

Si3452/3

High Volt age Interface

I2C

OTP

RAM

Mixe d Signal

Resources

PSE State

Machines

and

Measurement

Subsystem

Host

Controller I2C

4 Ports of PoE+

INT

SDA

SCL

RST

Si84xx Digital

Isolator

Si3452/3

INT

RST

SCL

SDA

VREF

Bidirectional

Isolator

Host / Switch

VDD DGNDAGND

DET4

DET3

DET2

DET1

VOUT1VOUT2VOUT3VOUT4

RBIAS

44.2 k

1% VEE

PORT1

PORT2

PORT3

PORT4

To Magnetics

GND12/34

VEE[4:1]

AD3

AD2

AD1

AD0

AD2

AD3

AD1

AD0

+3.3 V

Tie high

or low to

select

address

–54 V

1.1 V

(e.g. TLV431)

Si3452/3

12 Rev. 0.42

4. Functional Description

Integrating four independent high voltage PSE port interfaces, the Si3452/3 high voltage port controller enables an

extremely flexible solution for virtually any PoE or PoE+ PSE application. The Si3452/3 provides all of the high

voltage Power over Ethernet PSE functions.

Each port of the Si3452/3 integrates all high voltage PSE controller functions needed for a quad-port PoE design,

including the power MOSFET, efficient current sensing circuitry, transient voltage surge-suppressor, and multiple

detect and disconnect circuits. When the DC disconnect or dV/dt disconnect sensing methods are selected, the

external BOM is typically only a single filter capacitor on each high voltage port.

When a PD device has been properly detected and classified, the port is powered by a –54 V nominal supply with

continuous monitoring of voltage and current for feedback to the host system.

In addition to the required IEEE features, the Si3452/3 includes many additional features:

Per port current / voltage monitoring and measurement

Support for 1-Event and 2-Event classification algorithms

Start up in shutdown mode or auto mode

Alternative A (Endpoint) or Alternative B (Midspan) detection timing

4.1. Detection

The Si3452/3 has per-port signature detection that satisfies the IEEE Std 802.3™-2005 specifications. However, by

utilizing a 3-point voltage-forced detection method, the Si3452/3 yields robust recognition of valid and invalid

powered device (PD) signatures, properly identifying signatures often mischaracterized by other detection

techniques.

Figure 4. PSE Sequencing (3-point Detection Followed by 2-Event Classification

and Powerup)—Vport relative to GND

The detection circuitry performs the function of setting the output voltage on any channel to the proper value for

detection or classification, and then measuring the resulting line current.

A typical detection cycle consists of applying 4 V, then 8 V, and back to 4 V with the current limit set to 3 mA. The

current is measured after appropriate settling time. For a valid PD, the detection signature must be compliant with

the detection voltage both increasing and decreasing.

3 point

detection

2 event

classification

Port powerup

Si3452/3

Rev. 0.42 13

4.2. Classification

Following a successful PD detection, the classification phase will be automatically initiated in all operational

modes. During this phase a single measurement will be made at 18 V to determine how much power the PD device

will draw under maximum loads per the IEEE 802.3af and 802.3at standards. The current limit during this test

mode is 60 mA nominal.

The Si3452/3 supports 1-Event and 2-Event classification. When operating in PoE (<15.4 W) mode, 1-Event

classification is used. Operation in PoE+ (>15.4 W) mode results in 2-Event classification probes. The 1-Event

classification is compliant to IEEE standard 802.3-2005. 2-Event classification is compliant to draft IEEE P802.3at.

4.3. Port Turn-on and Power FETs

The FET is turned on with a gate drive that results in a very low-noise turn-on waveform with a slew rate of less

than 1 V/µsec (See Figure 5).

The power FET switch on each port has been sized to have a typical ON resistance of approximately 0.3 . The

shunt resistor for current measurement has also been set to 0.1 . Including interconnection and process variation,

the total resistance to VEE for a port that is on is 0.6  (max). This limits the maximum power dissipation per

channel to < 250 mW, when the operating current is 600 mA, the maximum current allowed by the IEEE 802.3at

PoE+ standard.

The FET has a programmable operating current limit. Each channel can be set to support output currents of

400 mA or 800 mA minimum.

In addition to the normal current limit, there is a short circuit current shutdown approximately 25% greater than the

nominal current limit. If there is a transient current surge where the current ramps up faster than the programmed

current limit can respond, the gate drive voltage is clamped immediately to VEE. The clamp is enabled for at least

10 µs, which allows the normal current circuitry to respond.

Another important protection feature is fold back current limiting. When VOUT is near VEE, the current limit is at

maximum. As the Vds of the driver switch increases (and VOUT is closer to ground) the current limit goes to its

lowest level. The amount of the fold back current is scaled proportionally with the programmed current limit.

Figure 5. Turn-On Waveform—Vport relative to GND

Si3452/3

14 Rev. 0.42

4.4. Disconnect Detection

4.4.1. dV/d t Disconnect (Si3452)

The dV/dt™ disconnect function can be used to detect a disconnected device without using dc disconnect or ac

disconnect.

In dV/dt™ disconnect mode, the FET current limit is switched to 7.5 mA. If the FET voltage increases, a load is

assumed to be present and the FET current limit is automatically switched back to its pre-selected value. If, after

350 ms, the FET voltage has not increased, there is no load present, and the FET is turned off.

In addition to operating in a manner functionally distinct from DC disconnect, dV/dt disconnect requires no

additional external components and fully interoperates with all powered device DC Maintain Power Signatures. For

more information, see "AN399: dV/dt Disconnect and the IEEE 802.3 PoE Standard".

4.4.2. DC Disconnect (Si3453)

The port current is continuously monitored by the Si3452/3. The Si3452/3 can dynamically change the

measurement scale to achieve accuracy over a wide range of currents.

As defined in the IEEE 802.3 PoE standard the PSE should disconnect if the port current is less than a nominal

7.5 mA for more than 350 ms.

4.5. Transient Voltage Surge Suppressio n

The Si3452/3 features robust on-chip surge protectors on each port; this is an industry first. This unique protection

circuitry acts as an active device which can withstand lightning transients as well as large ESD transient events.

When the port voltage exceeds its protection limit and the current reaches a triggering threshold, current is shunted

from the port to the ground pins.

Internal circuitry is provided to protect the line outputs from externally coupled fault currents. These are transient

currents of up to 5 A peak.

The operation of the protection circuits depends on the operating mode of the channel switch and the direction of

the fault current. The clamping operation is performed on the detect pin.

The switch itself will also be protected by the current limit. If the transient lasts long enough to heat up the die, then

the temperature sense circuit will shut off the switch, and all the fault current will flow through the clamp diode.

4.6. Temperature Sense

A temperature sense signal is used in conjunction with the current limit status signals from the gate drive blocks.

Any channel that is generating excess heat is assumed to be operating in current limit mode, with both high voltage

drop and high current.

If the port is in PoE mode, an overload will generally not result in thermal shutdown before the 60 ms ICUT period. If

the port is in PoE+ mode, an overload may cause the port to shut down prior to the 60 ms ICUT period. In either

case, the event is reported as ICUT

. The faster shutdown in PoE+ mode is consistent with and specifically allowed

by the 802.3at draft and provides much more robust overload protection than is possible with external FETs.

In addition, there is a thermal shutdown if the package temperature exceeds 120 °C. If this threshold is reached, all

output drivers are turned off and detection modes are disabled. This secondary threshold limit guards against the

possibility that the overheating is not caused by a driver operating in current limit.

4.7. Port Measurement and Monitoring

VEE monitoring in conjunction with port current monitoring allows measurement of port power. Port power

monitoring, dynamic power allocation via LLDP*, and port power policing allows efficient power supply sizing.

The Si3452/3 is factory calibrated and temperature compensated for the following measurements:

Port current measurement. These measurements are auto ranged and scaled to a 16 bit number at 100 uA per

bit. Port current accuracy is ±4% ± 2 mA.

VEE is measured with a scale of 64 V. The measurement is reported as a 16 bit number scaled at 1 mV per bit.

VEE measurement accuracy is ±4% over the valid VEE range.

*Note: LLDP = Link Layer Discovery Protocol. Refer to IEEE 802.3at (draft) and IEEE 802.1AB for more information.

Si3452/3

Rev. 0.42 15

4.8. SMBus/I2C Interface Details

The I2C interface is a two-wire, bi-directional serial bus. The I2C is compliant with the System Management Bus

Specification (SMBus), version 1.1, and compatible with the I2C serial bus. Reads and writes to the interface by the

system controller are byte oriented with the I2C interface autonomously controlling the serial transfer of the data. A

method of extending the clock-low duration is available to accommodate devices with different speed capabilities

on the same bus. The I2C interface may operate as a master and/or slave, and may function on a bus with multiple

masters. The I2C provides control of SDA (serial data), SCL (serial clock) generation and synchronization,

arbitration logic, and START/STOP control and generation.

A typical I2C transaction consists of a START condition followed by an address byte (Bits7–1: 7-bit slave address;

Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Each byte that is received (by a master

or slave) must be acknowledged (ACK) with a low SDA during a high SCL (see Figure 6). If the receiving device

does not ACK, the transmitting device will read a NACK (not acknowledge), which is a high SDA during a high

SCL.

The direction bit (R/W) occupies the least-significant bit position of the address byte. The direction bit is set to logic

1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation. All transactions are

initiated by a master, with one or more addressed slave devices as the target. The master generates the START

condition and then transmits the slave address and direction bit. If the transaction is a WRITE operation from the

master to the slave, the master transmits the data a byte at a time waiting for an ACK from the slave at the end of

each byte.

For READ operations, the slave transmits the data waiting for an ACK from the master at the end of each byte. At

the end of the data transfer, the master generates a STOP condition to terminate the transaction and free the bus.

Figure 6 illustrates a typical SMBus/I2C transaction.

Silicon Laboratories recommends the use of bidirectional digital isolators, such as the Si840x, to isolate the I2C

communications interface between the Si3452/3 high voltage port controllers and the system host controller.

Figure 6. Typical I2C Bus Tr ansactions

01 0A3A2A1A0R/W#

ACK b y IC

A7 A6 A5 A4 A 3 A2 A1 A 0

ACK by IC

D7 D6 D5 D4 D3 D2 D1 D0

ACK by IC ST OP by M aste rST ART

Fixed IC

Address

Pin Set IC

Addr ess

Slave Address Register Address Write Data

0 1 0 A3A2 A1A0R/W#

ACK b y IC

A 7 A6 A5 A4 A3 A 2 A1 A0

ACK by ICSTART

Fixed IC

Ad dr es s

Pin Set IC

Ad dr e ss

S lav e Ad d re ss R egi st er A dd re ss

Setup Register Addr ess

START

0 1 0 A3A2A1A0R/W#

ACK b y IC

D7 D6 D5 D4 D3 D2 D1 D0

Not ACK by Master

STOP by Master

Fixed IC

Address

Pi n Se t IC

Addr ess

Slave Address Register Data

Transfer Data to Setup Address

Write Sequ ence

Read Sequence

Si3452/3

16 Rev. 0.42

4.8.1. Address Pins

Pins with the same name must be externally connected and then tied high or low via a weak (10 k) pull up or pull

down to establish the device address at power up. The Si3452/3 powers up in either Auto mode or Shutdown mode

depending on the ordering part number. For more information, see "11. Ordering Guide" on page 32.

4.8.2. Address Format

The address byte of the I2C communication protocol has the following format:

Bit[0] R/W bit (0 = write, 1 = read)

Bit[1..4] the Si3452/3 address

Bit[5..7] 010b

The device will also respond to the global address 0x30

Table 15 lists the valid device addresses:

Table 14. Address Pin Assignment

Pin # Pin Name

21 AD3

24 AD3

25 AD2

26 AD2

27 AD1

28 AD0

34 AD0

36 AD1

Table 15. Address Selection

AD3 AD2 AD1 AD0 Address Valid

00000x20Y

00010x21Y

0010 — N

0011 — N

01000x24Y

01010x25Y

0110 — N

0111 — N

10000x28Y

10010x29Y

10100x2AY

10110x2BY

11000x2CY

11010x2DY

11100x2EY

11110x2FY

Si3452/3

Rev. 0.42 17

4.8.3. ARA

For I2C operation, the Si3452/3 provides an Alert Response Address to the master when the Slave address is

0x0C and the INT pin is asserted. When these conditions are met, this IC begins to provide its address followed by

a one. During this transaction, the IC monitors its SDA pin's level to determine if the read value matches what this

IC is writing on the SDA pin. If the value matches for the entire transfer, then the Si3452/3 de-asserts its INT pin. If

a mismatch is detected, the Si3452/3 immediately aborts the transaction and floats its SDA pin until the IC needs to

respond to another bus transaction) and continues to assert its INT.

Figure 7. ARA Transaction

After the INT pin is de-asserted, it is assumed the host will read the appropriate COR read registers to clear the

interrupt source. Any new interrupt source after the INT pin is cleared will not generate a new interrupt until the

original interrupt source is cleared.

5. Register Interface

The registers types are described in the following sections.

5.1. Interrupt (Registers 0x00–0x01)

An interrupt (INT pin low) is generated if any bit of the Interrupt register (register 0x00) is true. The Interrupt register

contains the information about which port is generating the interrupt or if the interrupt is due to a global event.

The port interrupt is generated by the port event register masked by the event mask register.

Port event = (tSTART event AND tSTART mask) OR (tICUT event AND tICUT mask) OR (CLASS_event AND

CLASS_mask) OR (DET_EVENT AND DET_MASK) OR (Pgood_event AND Pgood_MASK) OR (Penable_event

AND Penable_mask)

The device event bit of the Interrupt register is set if there is a VEE or a temperature event in register 0x1D.

5.2. Port Event (Registers 0x02–0x05)

This register contains bits that become true if the event has occurred. The registers are Clear On Read (COR) so

that reading these registers will clear the INT pin if the INT pin is being held low due to a port event.

“tSTART“ is an event bit indicating an overload occurred for all but 5 msec of the initial 60 msec start up time.

“tICUT“ is an event bit indicating an overload condition has existed for greater than 60 msec after the first 60 msec.

tICUT has a 16:1 up down counter so that if the overload is present at less than a 6.66% cycle the port will not shut

down. Overload is defined as I>ICUT or port voltage not within 2 V of VEE. The port is turned off on this event. A

tICUT event is also generated if the port is shutdown due to an overload or due to the protection clamp turning on. If

the port is set to auto mode it will attempt to re-power after >750 msec if there is a good detection signature.

“Rgood CLS“ indicates classification has been completed. Classification is only attempted after an Rgood so if this

bit is set it indicates detection gave an Rgood and classification is complete.

Transfer Data to Setup Address

ARA Slave Address IC’s Address

Fixed IC Address STOP by Master

Pin Set IC Address

ACK by IC

R/W#0011000

START

0 1 0A3A2A1A01

Not ACK by Master

Si3452/3

18 Rev. 0.42

“DET compl“ indicates the completion of a detection cycle. Normally this bit will be masked. The DET complete bit

would be used for legacy detection via modified link pulses. If the link pulse is returned indicating a PD is present

then normally a detection is done and the port is powered only if the result is not a short. In some cases it may be

desirable to deny power to a port where an overload has been detected until the port is unplugged. In this case, the

Ropen result will be used to indicate the port has been unplugged and detection and classification can resume.

“Disconnect event“ indicates a disconnect has occurred. DC power was removed due to the dV/dt™ or DC

disconnect. Overload conditions or loss of VEE turns off ports but does not generate a disconnect event.

“Pgood“ indicates the port has been turned on and did not shut down during the Tstart time.

“Penable“ indicates a port has been turned on.

5.3. Port Status (Registers 0x06–0x09)

These registers specify the port status. They are read only.

“Pwr good“ indicates the port has been turned on, and the port voltage is within 2 V of VEE.

“Pwr Enable“ indicates the port has been turned on.

The 3 class status bits indicate the last classification result for that port. If a classification has not been done or if

the port is shutdown with no new classification result, the class status is reported as unknown.

The 3 detect status bits indicate the last detection result for that port. If a detection has not been done or if the port

is shutdown with no new detection result, the detection status is reported as unknown.

5.4. Port Configuration (Registers 0x0A–0x011)

These registers indicate the port configuration. They are read/write.

The “PoE+“ bit specifies the dc current limit at either 425 mA or 850 mA nominal.

“Disconnect enable“ must be set for power to be removed if there is a disconnect. The disconnect type (based on

dc disconnect or based on Silicon Laboratories proprietary dV/dt disconnect) is determined by the ordering part

number.

“Port mode“ is set according to the following table.

ICUT is the nominal current level at which the port will automatically power down if ICUT is exceeded for 60 msec. It

can be set with 3.2 mA resolution. The accuracy of current measurement is approximately 5% so ICUT is normally

set 7% higher than the supported current level. ICUT is automatically set based on the classification result and

PoE+ mode. The automatically set ICUT level is appropriate for a 44 V minimum system power supply for classes

0–3 and for a 50 V minimum power supply for PoE+ mode.

If the Si3452/3 is in the semi-auto mode, ICUT will not be updated according to the classification result. This means

that if it is desired to set ICUT at port turn on, this should be done before the port is turned on.

Table 16. Port Mode Selection

Port Mode Setting

B1, B0 Mode Description

00b Shutdown The power is shutdown with no detection pulses. A command to

manually power the port is ignored.

01b Manual The port can be powered by the manual power command.

10b Semiauto Detection is done and classification is done for Rgood but the port

does not power.

11b Auto

Detection Classification and Port powering are all automatic with no

host intervention required. ICUT and ILIM are automatically set

according to the PoE+ mode and classification result.

Si3452/3

Rev. 0.42 19

Once a port is turned on, ICUT can be changed dynamically. It is often un-desirable to use a low value of ICUT

during port turn on because inrush can trigger the ICUT event. For this reason, it is normal to allow the port to turn

on with the automatic ICUT setting and then later change this value after port current has stabilized and also if the

PD and PSE have negotiated for a different ICUT value based on the PoE L2 power negotiation protocol (LLDP).

The Si3452/3 supports 2-Event classification as defined in the IEEE 802.3at draft. 2-event classification is an

alternative to L2 power management where the PSE advertises it is capable of PoE powering by generating two

classification pulses. 2-Event classification is only supported for auto mode. If the Si3452/3 is in auto mode and the

first event classification result is class 4, the mark, second event and second mark are performed. Power is applied

only if the second event is also class 4. If the second event is not class 4, the classification error is reported and the

port will not power.

If the port is in manual mode, classification is done prior to turning on the port. It is not possible to turn on a port

that gives classification overload or gives unequal results for 2-Event classification.

5.5. Command and Return Registers (Registers 0x12–0x1C)

The global command register enables manual port turn on or turn off, chip reset, port reset and measurement of

port current and VEE. It is a Write only register. See Table 23 on page 23 for a list of all available commands.

If the command results in a numerical return value, that value is stored in the measurement registers which are

read only. Each of the five possible measurements results in a 2 byte return value and that value is stored in a

unique register. VEE is encoded in mV units so the full scale is 65.535 V and Iport is encoded in 100 µA units so the

full scale is 6.5535 A.

The data for the return value is only updated after a command. This means, that the numerical value of the port

current or VEE voltage in the measurement register will be the value at the time the command was issued. If the

port turns off due to an overload or disconnect the port current register contents will not be set to zero. If a

command to read port current is issued and the port is off, the return value will be zero.

5.6. Device Status Register (0x1D)

The device event bits are listed in Table 17.

The Device status register is RO. The VEE, UVLO, and overtemp bits reflect the device status. They are set if VEE

or temperature is out of range and reset if the VEE or temperature is in range. Bit 6 of the Interrupt register is set if

there is a change in the overtemp status (bit 6 of 0x1D), and bit 5 of the Interrupt register is set if there is a change

in the VEE UVLO status (bit 5 of 0x1D). Reading register 0x1D clears these bits of the Interrupt register but does

not clear the device status register.

In addition, bit B0 indicates whether or not detection back off is used. For PSEs that are wired as Alternative B

(power on the spare pair, typically used for midspans), the time between detection pulses is increased to slightly

over two seconds to avoid interference with Alternative A (power on the data pair, typically used for endpoints). Bit

B0 can be toggled using the command code 0x10.

Table 17. Device Status Bits

Bit Description

B6 - OverTemp

The Si3452/3 has per port thermal shutdown sensors as well a global thermal shutdown

at a slightly higher temperature. The global thermal shutdown bit of the device event

B5 - VEE UVLO VEE UVLO. The part is put in it’s reset state if VEE is not in a valid range.

Si3452/3

20 Rev. 0.42

Table 18. Si3452/3 Register Map

Address Register Name Type B7 B6 B5 B4 B3 B2 B1 B0 POWER_UP

Interrupts

0x00 Interrupt Reg 1 RO Overtemp

change

VEE UVLO

change Port 4 event Port 3 event Port 2 event Port 1 event 0x00

0x01 Interrupt Mask 1 RW Device sta-

tus mask tSTART mask tICUT mask Rgood CLS mask DET compl mask Disconnect

mask PwrGood mask PwrEn mask 0x85

Port Events

0x02 Port 1 Events COR tSTART Event tICUT Event Rgood CLS DET compl Disconnect Ev PwrGood

Change

PwrEn

Change 0x00

0x03 Port 2 Events COR tSTART Event tICUT Event Rgood CLS DET compl Disconnect Ev PwrGood

Change

PwrEn

Change 0x00

0x04 Port 3 Events COR tSTART Event tICUT Event Rgood CLS DET compl Disconnect Ev PwrGood

Change

PwrEn

Change 0x00

0x05 Port 4 Events COR tSTART Event tICUT Event Rgood CLS DET compl Disconnect Ev PwrGood

Change

PwrEn

Change 0x00

Status

0x06 Port 1 Status RO PwrGood

Status

PwrEnable

Status CLS Stat B2 CLS Stat B1 CLS Stat B0 DET Stat B2 DET Stat B1 DET Stat B0 0x00

0x07 Port 2 Status RO PwrGood

Status

PwrEnable

Status CLS Stat B2 CLS Stat B1 CLS Stat B0 DET Stat B2 DET Stat B1 DET Stat B0 0x00

0x08 Port 3 Status RO PwrGood

Status

PwrEnable

Status CLS Stat B2 CLS Stat B1 CLS Stat B0 DET Stat B2 DET Stat B1 DET Stat B0 0x00

0x09 Port 4 Status RO PwrGood

Status

PwrEnable

Status CLS Stat B2 CLS Stat B1 CLS Stat B0 DET Stat B2 DET Stat B1 DET Stat B0 0x00

Configuration

0x0A Port 1 Config RW PoE+ Discon En Port Mode B1 Port Mode B0 00000100b

0x0B Port 2 Config RW PoE+ Discon En Port Mode B1 Port Mode B0 00000100b

0x0C Port 3 Config RW PoE+ Discon En Port Mode B1 Port Mode B0 00000100b

0x0D Port 4 Config RW PoE+ Discon En Port Mode B1 Port Mode B0 00000100b

0x0E Port 1 ICUT RW B7 B6 B5 B4 B3 B2 B1 B0 0x75

0x0F Port 2 ICUT RW B7 B6 B5 B4 B3 B2 B1 B0 0x75

0x10 Port 3 ICUT RW B7 B6 B5 B4 B3 B2 B1 B0 0x75

0x11 Port 4 ICUT RW B7 B6 B5 B4 B3 B2 B1 B0 0x75

Si3452/3

Rev. 0.42 21

Global Device

0x12 Command Reg-

ister WO CMD Code B2 CMD Code B1 CMD Code B0 CMD Param

CMD Param

B0 0x00

0x13 VEE MSB RO 0x00

0x14 VEE LSB RO 0x00

0x15 Current P1

MSB RO 0x00

0x16 Current P1 LSB RO 0x00

0x17 Current P2

MSB RO 0x00

0x18 Current P2 LSB RO 0x00

0x19 Current P3

MSB RO 0x00

0x1A Current P3 LSB RO 0x00

0x1B Current P4

MSB RO 0x00

0x1C Current P4 LSB RO 0x00

0x1D Device Status RO OverTemp VEE UVLO Alternative B

Timing 0x00

Revision

0x60 Hardware

Revision RO

0x61 Firmware Revi-

sion RO

0x62 Firmware Revi-

sion RO

0x63 Firmware Revi-

sion RO

Table 18. Si3452/3 Register Map (Continued)

Address Register Name Type B7 B6 B5 B4 B3 B2 B1 B0 POWER_UP

Si3452/3

22 Rev. 0.42

Table 19. Si3452/3 Detect Encoding

Value Condition

000b Unknown

001b Short

010b Reserved

011b RLOW

100b Good

101b Rhigh

110b Ropen

111b Reserved

Table 20. Si3452/3 Class Encoding

Value Condition

000b Unknown

001b Class 1

010b Class 2

011b Class 3

100b Class 4

101b Probes Not Equal

110b Class 0

111b Class Overload

Table 21. Si3452/3 Port Mode Encoding

Value Condition

00b Shutdown

01b Manual

10b Semiauto

11b Auto

Si3452/3

Rev. 0.42 23

Table 22. Si3452/3 Port Configuration

PoE+ bit Class Auto Mode Setting of

ICUT Register ICUT Nominal Ilim Nominal*

0 or 1 don’t care 1 0x1E 97 mA 425 mA

0 or 1 don’t care 2 0x35 170 mA 425 mA

0 or 1 don’t care 0/3 0x75 375 mA 425 mA

0 4 0x75 375 mA 425 mA

1 4 0xC9 640 mA 850 mA

*Note: During initial port turn-on (TSTART time of 60 msec), the current limit is set to 425 mA, even in PoE+ mode.

Table 23. Si3452/3 Command Codes

Command Command

Codes CMD

Parameter 2 Byte Return Value

Power on port 0x01 0x04 | port no 001b 2 bit port number

Power off port 0x02 0x08 | port no 010b 2 bit port number

Reset port 0x03 0x0C | port no 011b 2 bit port number

Toggle detection

back-off timing*0x04 0x10 100b NA

Reset chip 0x05 0x14 101b NA

Get VEE 0x06 0x18 110b NA VEE in mV units

Read port current 0x07 0x1C | port no 111b 2 bit port number Port current in 100 µA

units

*Note: This command toggles bit 0 or Register 0x10. When bit zero is set, the detection back-off of 2 seconds is implemented

(alternative B or “midspan” mode).

Si3452/3

24 Rev. 0.42

6. Operational Notes

6.1. Port Turn On

Ports are normally powered by either putting the Si3452 in the auto mode and allowing the Si3452 to control the

powering sequence, or by putting the Si3452 in the manual mode and issuing a turn-on command.

If the port is turned on by putting it in auto mode, the Si3452/3 will take care of all specified timing, and it will take

care of the two-event classification if the first event result is class 4 and PoE+ mode is enabled. However, if

automatic mode operation is not desired after port turn on, the port should be set to semi-auto or manual mode

once it has powered.

If the port is turned on by putting it in manual mode, the normal sequence is to start with the port in semi auto mode

and interrupt on a classification complete, which indicates that there is a valid PD signature and a classification

result is available. Based on the classification result, the host can make a decision to apply power or not. The IEEE

standard requires that a port be powered within 400 msec of a valid detect complete. It is also desirable to power

the port prior to the start of the next detection pulse, which can occur in as little as 300 msec. Therefore, it is

recommended that ports be powered in under 250 msec from the class complete interrupt when using the manual

mode turn on command.

Using manual mode turn-on, detection is not done prior to port turn on, but classification is always performed just

prior to port turn on. A port that presents an invalid classification signature will not be turned on. 2-event

classification is performed if the first event result is class 4 and the port is enabled for PoE+ mode. The port is not

turned on if the classification result is overload or if PoE+ mode is enabled and the second event result is not class

4. The manual mod classification step does not generate a classification complete flag because it is assumed that

the classification was already done in semi-auto mode, and the host has already made the decision to grant power.

If a port turn-on command is issued in semi-auto or auto mode, the port will power, but this is not desireable

because IEEE-compliant timing is not assured.

6.2. Changing the Interrupt Mask

The INT register and INT pin are always synchronized. However, there can be up to a 5 msec delay between an

event that causes or clears an interrupt and the update of the register and pin.

Thus, if the INT mask register is changed to clear an interrupt or to block an interrupt source, there can be up to a

5 msec delay between the change of the INT mask register and the resultant change in the INT register and INT

pin.

Generally, use of the mask register to clear interrupts is not recommended; it is better to clear an interrupt by

reading the appropriate COR register.

Si3452/3

Rev. 0.42 25

7. PCB Layout Guidelines

Due to the high current of up to 800 mA per port, the following board layout guidelines apply. In addition, contact

Silicon Laboratories. for access to complete PSE reference design databases including recommended layouts.

The VEE1, VEE2, VEE3 and VEE4 pins can carry up to 800 mA and are connected to a VEE bus. The VEE bus for

a 24 port PCB layout could thus carry as much as 20 A current. With 2 oz. copper on an outer layer, a bus of 0.4

inches is needed. For an inner layer, this increases to 1 inch wide bus. Use of large or multiple vias is required for

properly supporting the 800 mA per channel operating current. The VEE pin does not carry high current and can be

connected directly to the bus as well. The best practice is to devote an entire inner layer for VEE power routing.

Similarly, GND1/2 and GND3/4 pins can carry up to 1.6 A per pin and the GND return bus should be at least as

wide as the VEE bus as above. The best practice is to devote an entire inner layer for ground power routing. The

ground power plane does not generally have a high frequency content (other than external faults) so it is generally

acceptable to use the ground power plane as a ground signal plane and tie AGND and GND12, GND34 to this

plane as well.

The VOUTn pins carry up to 800 mA dc and up to 5 A in faults, so a 20 mil trace with wide or multiple vias are also

recommended. The VDETn pins also carry fault current so this pin connection to VOUTn needs to use 20 mil

traces and wide or multiple vias where needed.

The VDD currents are not large so it is acceptable to route the VDD nodes on one of the outer layers.

If care is taken to avoid disruption of the high current paths, VDD can be globally routed on one of the power planes

and then locally routed on an inner or outer layer.

To avoid coupling between surge events and logic signals, it is recommended that VOUTn traces be routed on the

opposite side as the I2C interface pins.

The thermal pad of the Si3452/3 is connected to VEE. At full IEEE 802.3at current of 600 mA on each port the

dissipation of the Si3452/3 is up to 1.2 W; so, multiple vias are required to conduct the heat from the thermal pad to

the VEE plane. As many as 36 small vias provide the best thermal conduction.

Si3452/3

26 Rev. 0.42

8. Pin Descriptions

Table 24. Si3452/3 Pin Descriptions

Pin # Name Type Description

1 VEE1 Supply Driver 1 VEE supply. Short to VEE, VEE2/3/4.

2 VEE Supply Global PoE (–48 V nom.) or PoE+ (–54 V nom.) supply. Short to VEE1/2/3/4.

3 VREF Analog input 1.1 V nom. voltage reference from reference generator (for example, TLV431 or

power management unit).

4 AIN Analog input Measurement data converter input. Short to AOUT.

5 AOUT Analog output Measurement multiplexer subsystem output. Short to AIN.

6 AGND Ground Analog ground reference. Short to AGND pin 8, GND12/34, DGND.

7 RBIAS Analog input External 44.2 kΩ (±1%) resistor to ground sets internal bias currents.

8 AGND Ground Analog ground reference. Short to AGND pin 6, GND12/34, DGND.

9 NC No connect Do not connect (float).

10 VEE4 Supply Driver 4 VEE supply. Short to VEE, VEE1/2/3.

11 NC No connect Do not connect (float).

12 VOUT4 Analog I/O Port 4 power FET switch output. When on, provides a low impedance path to

VEE4.

13 DET4 Analog I/O Connection for port 4 detection, classification, and transient surge protection. This

pin is tied to VOUT4.

VEE

VEE1

AIN

RBIAS

VREF

AGND

AOUT

AGND 8

DGND

VDD

AD1

AD3

AD0

AD2

VOUT4

SDA

DET4

SCL

GND34

DET3 18

VDD 19

VOUT1

INT

DET1

AD0

RST

GND12

AD1

DET2

VEE4 10

NC 9VEE3

RST

AD3

VOUT3 20

32 VOUT2

31 VEE2

Si3452

(Top View)

Si3452/3

Rev. 0.42 27

14 SDA Digital I/O I2C data pin

15 GND34 Ground Ground supply for protection clamps. Short to AGND, GND12, DGND.

16 SCL Digital I/O I2C clock pin

17 NC No connect Do not connect (float).

18 DET3 Analog I/O Connection for port 3 detection and classification. See DET4 for detailed descrip-

tion.

19 VDD Supply +3.3V (±10%) isolated supply. Short to VDD pin 30.

20 VOUT3 Analog I/O Port 3 power FET switch output. When on, provides a low impedance path to

VEE3.

21 AD3 Digital I/O Chip address bit 3 pin, read after reset. Address set with defined resistor dividers.

Pin also used for internal communications. Short to AD3 pin 24.

22 VEE3 Supply Driver 3 VEE supply. Short to VEE, VEE1/2/4.

23 RST Digital input Active low digital reset. Short to RST pin 38.

24 AD3 Digital I/O Chip address bit 3 pin, read after reset. Address set with a 10 kpull-up or pull-

down resistor. Also used for internal communications. Short to AD3 pin 21.

25 AD2 Digital I/O Chip address bit 2 pin, read after reset. Address set with a 10 kpull-up or pull-

down resistor. Also used for internal communications. Short to AD2 pin 26.

26 AD2 Digital I/O Chip address bit 2 pin, read after reset. Address set with a 10 kpull-up or pull-

down resistor. Also used for internal communications. Short to AD2 pin 25.

27 AD1 Digital I/O Chip address bit 1 pin, read after reset. Address set with a 10 kpull-up or pull-

down resistor. Also used for internal communications. Short to AD1 pin 36.

28 AD0 Digital I/O Chip address bit 0 pin, read after reset. Address set with a 10 kpull-up or pull-

down resistor. Also used for internal communications. Short to AD0 pin 34.

29 DGND Ground Digital ground reference. Short to AGND, GND12/34

30 VDD Supply +3.3 V isolated supply. Short to VDD pin 19.

31 VEE2 Supply Driver 2 VEE supply. Short to VEE, VEE1/3/4.

32 VOUT2 Analog I/O Port 2 power FET switch output. When on, provides a low impedance path to

VEE2.

33 DET2 Analog I/O Connection for port 2 detection and classification. See DET4 for detailed descrip-

tion.

34 AD0 Digital I/O Chip address bit 0 pin. See description for- and short to AD0 pin 28.

35 GND12 Ground Ground supply for protection clamps. Short to AGND, GND34, DGND.

36 AD1 Digital I/O Chip address bit 1 pin. See description for- and short to AD1 pin 27.

37 DET1 Analog I/O Connection for port 1 detection and classification. See DET4 for detailed descrip-

tion.

38 RST Digital input Active low digital reset. Short to RST pin 23.

Table 24. Si3452/3 Pin Descriptions (Continued)

Pin # Name Type Description

Si3452/3

28 Rev. 0.42

39 VOUT1 Analog I/O Port 1 power FET switch output. When on, provides a low impedance path to

VEE1.

40 INT Digital output Active low interrupt output pin.

Table 24. Si3452/3 Pin Descriptions (Continued)

Pin # Name Type Description

Si3452/3

Rev. 0.42 29

9. Package Outline: 40-Pin QFN

The Si3452/3 is packaged in an industry-standard, RoHS compliant 6 x 6 mm2, 40-pin QFN package.

Figure 8. 40-Pin QFN Mechanical Diagram

Table 25. Package Diagram Dimensions

Dimension Min Nom Max

A 0.80 0.85 0.90

A1 0.00 0.02 0.05

b 0.18 0.25 0.30

D 6.00 BSC.

D2 3.95 4.10 4.25

e 0.50 BSC.

E 6.00 BSC.

E2 3.95 4.10 4.25

L 0.30 0.40 0.50

aaa 0.10

bbb 0.10

ccc 0.08

ddd 0.10

eee 0.05

Notes:

1. All dimensions shown are in millimeters (mm) unless otherwise noted.

2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.

3. This drawing conforms to JEDEC outline MO-220, Variation VJJD-2

4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification

for Small Body Components.

Si3452/3

30 Rev. 0.42

10. Recommended PCB Footprint

Figure 9. PCB Land Pattern

Table 26. PCB Land Pattern Dimensions

Dimension Min Max

e 0.50 BSC

E5.42 REF

D5.42 REF

E2 4.00 4.20

D2 4.00 4.20

GE 4.53 —

GD 4.53 —

X — 0.28

Y0.89 REF

ZE — 6.31

Si3452/3

Rev. 0.42 31

ZD — 6.31

Notes:

General

1. All dimensions shown are in millimeters (mm) unless otherwise noted.

2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification.

3. This Land Pattern Design is based on IPC-SM-782 guidelines.

4. All dimensions shown are at Maximum Material Condition (MMC). Least Material

Condition (LMC) is calculated based on a Fabrication Allowance of 0.05 mm.

Solder Mask Design

5. All metal pads are to be non-solder mask defined (NSMD). Clearance between the

solder mask and the metal pad is to be 60 µm minimum, all the way around the pad.

Stencil Design

6. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should

be used to assure good solder paste release.

7. The stencil thickness should be 0.125 mm (5 mils).

8. The ratio of stencil aperture to land pad size should be 1:1 for the perimeter pads.

9. A 4x4 array of 0.80 mm square openings on 1.05 mm pitch should be used for the

center ground pad.

Card Assembly

10. A No-Clean, Type-3 solder paste is recommended.

11. The recommended card reflow profile is per the JEDEC/IPC J-STD-020C

specification for Small Body Components.

Table 26. PCB Land Pattern Dimensions (Continued)

Dimension Min Max

Si3452/3

32 Rev. 0.42

11. Ordering Guide

11.1. Evaluation Kits and Reference Designs

Ordering Part

Number1Detect

Timing Power

Supported2Powerup

Mode3Disconnect

Method Firmware

Revision Package4 and

Temp. Range

Si3452-B01-GM Configurable Configurable Shutdown dV/dt™ discon-

nect

01 40-pin

6mm  6mm

QFN.

–10 to 85 °C

ambient

operating tem-

perature.

Si3452A-B01-GM Endpoint PoE (15.4W) Auto

Si3452B-B01-GM Midspan

Si3452C-B01-GM Endpoint PoE+ (30W)

Si3452D-B01-GM Midspan

Si3453-B01-GM Configurable Configurable Shutdown DC disconnect

Si3453A-B01-GM Endpoint PoE (15.4W) Auto

Si3453B-B01-GM Midspan

Si3453C-B01-GM Endpoint PoE+ (30W)

Si3453D-B01-GM Midspan

Notes:

1. Add “R” to the end of the ordering part number to denote tape-and-reel option. E.g., Si3452-B01-GMR.

2. The maximum PoE or PoE+ power applies to all ports on Auto mode devices.

3. Devices powering up into shutdown mode are intended for use with a system host that provides run-time configuration

or power-management.

4. All packages are RoHS and Pb-free.

Part Number Populated

Device Description Related Ethernet

Chipset Type

Si3452MS8-KIT Si3452-B01 PoE+ 8-port Midspan PSE evalua-

tion kit. Includes PC-control inter-

face, PD loads, cables.

None Evaluation Kit

Si3452V1-EVB Si3452-B01 PoE/PoE+ 24-port daughtercard Vitesse Reference Design

Si3452V2-EVB Si3452-B01 PoE+ 8-port Gb-Ethernet switch Vitesse SparX-G8e Reference Design

Si3452M1-EVB Si3452-B01 PoE/PoE+ 24-port daughtercard Marvell Reference Design

Si3452/3

Rev. 0.42 33

12. Device Marking Diagram

Figure 10. Device Marking Diagram

Table 27. Device Marking Table

Line # Text Value Description

1 Si3452 Base part number. This is not the “Ordering Part Number” since it does not contain a

specific revision. Refer to "11. Ordering Guide" on page 32.

for complete ordering information.

2 XYY X = Device revision.

YY = Firmware revision.

2 GM Device type. GM = Industrial temp range;

RoHS and lead-free device.

3 TTTTTT Trace code – assigned by the assembly subcontractor.

4 O Pin 1 identifier.

YY Assembly year

WW Assembly week.

Si3452/3

34 Rev. 0.42

DOCUMENT CHANGE LIST

Revision 0.4 to Revision 0.41

VEE UVLO only. Due to the protection clamp, OVLO

is not supported.

Updated thermal information.

Removed support for pin-selectable auto mode

powerup.

Changed device status to device event flags in

Interrupt register.

Si3452 is dv/dt™ disconnect, and Si3457 is DC

disconnect.

Added "6. Operational Notes" on page 24.

Updated "11. Ordering Guide" on page 32.

Added "11.1. Evaluation Kits and Reference

Designs" on page 32.

Revision 0.41 to Revision 0.42

Updated Vdd typical current.

Updated logical levels.

Clarified port turn on commands

Made reset timing “TBD”. The timing for samples is

approximately 50 msec. There is an objective to

improve this, but the final reset time has not yet been

established.

Si3452/3

Rev. 0.42 35

NOTES:

Si3452/3

36 Rev. 0.42

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Tel: 1+(512) 416-8500

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Email:PoEinfo@silabs.com

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