CP2108 Data Sheet
The CP2108 is a highly integrated USB to Quad UART Bridge
Controller providing a simple solution for updating RS-232/
RS-485 designs to USB using a minimum of components and
PCB space.
The CP2108 includes a USB 2.0 full-speed function controller, USB transceiver, oscilla-
tor, EEPROM, and four asynchronous serial data buses (UART) with full modem con-
trol signals in a compact 9 mm x 9 mm 64-pin QFN package. The on-chip EEPROM
may be used to customize the USB Vendor ID (VID), Product ID (PID), product descrip-
tion string, power descriptor, device release number, interface strings, device serial
number, modem and GPIO configuration as desired for applications. All customization
and configuration options can be selected using a simple GUI-based configurator. By
eliminating the need for complex firmware and driver development, the CP2108 devi-
ces enable quick USB connectivity with minimal development effort.
CP2108 is ideal for a wide range of applications, including the following:
KEY FEATURES
No firmware development required
Simple GUI-based configurator
Integrated USB transceiver; no external
resistors required
Integrated clock; no external crystal
required
USB 2.0 full-speed compatible
Four independent UART interfaces
16 GPIOs with configurable options
Royalty free Virtual COM port (VCP)
drivers
Instrumentation
Industrial control
Servers
Point-of-Sale products
CP2108
80 MHz
Oscillator
VBUS
D+
D-
GND
USB
Connector
(3.0 V to VDD)
UARTn (0-3)
USB Interface
Peripheral
Function
Controller
Full-Speed
12 Mbps
Transceiver
EEPROM
(Product Customization)
Handshake Control 6
RX(0-3)
TX(0-3)
RTS(0-3)
CTS(0-3)
DTR(0-3)
DSR(0-3)
RI(0-3)
DCD(0-3)
Clock Divider
VREGIN
VDD
VSS
VIO
VBUS
D+
D-
I/O Power and Logic Levels UART0-2, GPIO, SUSPEND, RESET
18
/SUSPEND
GPIO.0 – GPIO.15
SUSPEND
Voltage
Regulator
/RESET
Baud Rate
Generator
Connect to VBUS or
External Supply
Data
FIFO
UART0
UART1
UART2
UART3
(2.7 to 6.0 V)
VIO
High Drive UART 3(Pins 1-6)
VIOHD
silabs.com | Building a more connected world. Rev. 1.2
1. Feature List and Ordering Information
2108 BR
Tape and Reel (Optional)
Firmware Revision
Hardware Revision
03
CP GM
Package Type — QFN64
Temperature Grade — –40 to +85 °C (G)
Silicon Labs Xpress Product Line
Interface Family, USB-to-Quad-UART Bridge
Figure 1.1. CP2108 Part Numbering
The CP2108 devices have the following features:
Single-Chip USB-to-QUAD UART Data Transfer
Four independent UART interfaces
Integrated USB transceiver; no external resistor required
Integrated clock; no external crystal required
Integrated programmable EEPROM for storing customiza-
ble product information
On-chip power-on reset circuit
On-chip voltage regulator: 3.3 V output
USB Peripheral Function Controller
USB Specification 2.0 compliant; full-speed (12 Mbps)
USB suspend states supported via SUSPEND pins
Virtual COM Port Drivers
Works with existing COM port PC applications
Royalty-free distribution license
Supported on Windows, Mac, and Linux
Supply Voltage
Self-powered: 3.0 to 3.6 V
USB bus powered: 4.0 to 5.5 V
VIO voltage: 3.0 to VDD
VIOHD voltage: 2.7 to 6 V
UART Interface Features
Each UART interface supports the following:
Supports hardware flow control (RTS/CTS)
Supports all modem control signals
Data formats supported:
Data bits: 5, 6, 7, and 8
Stop bits: 1, 1.5, and 2
Parity: odd, even, set, mark and none
Baud rates: 300 bps to 2 Mbps
UART 3 (pins 1–6) supports interfacing to devices up to 6 V
GPIO Interface Features
Total of 16 GPIO pins with configurable options
Suspend pin support
Usable as inputs, open-drain or push-pull outputs
4 configurable clock outputs for external devices
RS-485 bus transceiver control
Toggle LED upon transmission
Toggle LED upon reception
Package Options
RoHS-UART 3 compliant 64-pin QFN (9x9 mm)
Temperature Range
–40 to +85 °C
Ordering Part Number
CP2108-B03-GM
CP2108 Data Sheet
Feature List and Ordering Information
silabs.com | Building a more connected world. Rev. 1.2 | 2
Table of Contents
1. Feature List and Ordering Information ......................2
2. System Overview ..............................5
3. Electrical Specifications ...........................6
3.1 Electrical Characteristics ..........................6
3.1.1 Recommended Operating Conditions ....................6
3.1.2 UART, GPIO, and Suspend I/O Electrical Characteristics .............7
3.1.3 GPIO ...............................7
3.1.4 Reset Electrical Characteristics ......................8
3.1.5 Voltage Regulator ..........................8
3.1.6 USB Transceiver ...........................9
3.2 Absolute Maximum Ratings .........................10
3.3 Thermal Conditions ............................11
3.4 Throughput and Flow Control.........................11
4. Pin Definitions ..............................12
5. QFN64 Package Specifications........................ 16
5.1 QFN64 Package Dimensions.........................16
5.2 QFN64 PCB Land Pattern ..........................18
5.3 QFN64 Package Marking ..........................19
6. Typical Connection Diagrams ........................20
7. USB Function Controller and Transceiver ...................23
8. Asynchronous Serial Data Bus (UART) Interfaces ................24
8.1 Baud Rate Generation ...........................24
9. GPIO and UART Pins ...........................25
9.1 GPIO — Alternate Clock Outputs .......................25
9.2 GPIO — Transmit and Receive Toggle .....................26
9.3 RS-485 Transceiver Bus Control .......................27
9.4 Hardware Flow Control (RTS and CTS) .....................28
9.5 High Drive Pins UART 3 Pins 1–6 .......................29
10. Internal EEPROM ............................30
11. CP2108 Device Drivers ..........................32
11.1 Virtual COM Port (VCP) Drivers .......................32
11.2 Driver Customization ...........................32
11.3 Driver Certification ............................32
12. Relevant Application Notes and Software ...................33
13. Revision History............................. 34
silabs.com | Building a more connected world. Rev. 1.2 | 3
13.1 Revision 1.2 ..............................34
13.2 Revision 1.1 ..............................34
13.3 Revision 1.0 ..............................34
13.4 Revision 0.1 ..............................34
silabs.com | Building a more connected world. Rev. 1.2 | 4
2. System Overview
The CP2108 is a highly integrated USB-to-Quad-UART Bridge Controller providing a simple solution for updating RS-232/RS-485 de-
signs to USB using a minimum of components and PCB space. The CP2108 includes a USB 2.0 full-speed function controller, USB
transceiver, oscillator, EEPROM, and four asynchronous serial data buses (UART) with full modem control signals in a compact 9 x 9
mm QFN-64 package (sometimes called “MLF” or “MLP”).
The on-chip EEPROM may be used to customize the USB Vendor ID (VID), Product ID (PID), Product Description String, Power De-
scriptor, Device Release Number, Interface Strings, Device Serial Number, Modem, and GPIO configuration as desired for OEM appli-
cations. The EEPROM is programmed on-board via the USB, allowing the programming step to be easily integrated into the product
manufacturing and testing process.
Royalty-free Virtual COM Port (VCP) device drivers provided by Silicon Labs allow a CP2108-based product to appear as four COM
ports in PC applications. The CP2108 UART interfaces implement all RS-232/RS-485 signals including control and handshaking, so
existing system firmware does not need to be modified. The device also features a total of sixteen GPIO signals that can be user-de-
fined for status and control information. See www.silabs.com/appnotes for the latest application notes and product support information
for the CP2108.
An evaluation kit for the CP2108 is available. It includes a CP2108-based USB-to-UART/RS-232 evaluation board, a complete set of
VCP device drivers, USB and RS-232 cables, and full documentation. Contact a Silicon Labs sales representative or go to www.si-
labs.com/products/interface/Pages/CP2108EK.aspx to order the CP2108 Evaluation Kit.
CP2108 Data Sheet
System Overview
silabs.com | Building a more connected world. Rev. 1.2 | 5
3. Electrical Specifications
3.1 Electrical Characteristics
All electrical parameters in all tables are specified under the conditions listed in 3.1.1 Recommended Operating Conditions, unless sta-
ted otherwise.
3.1.1 Recommended Operating Conditions
VDD= 3.0 to 3.6 V, –40 to +85 °C unless otherwise specified.
Table 3.1. Recommended Operating Conditions1
Parameter Symbol Test Condition Min Typ Max Unit
Operating Supply Voltage VDD VDD 3.0 3.6 V
Operating Supply Voltage VRE-
GIN2
VREGIN 4.0 5.5 V
Operating Supply Voltage VIO VIO 3.0 VDD V
Operating Supply Voltage VIOHD VIOHD 2.7 6.0 V
Supply Current—Normal 3 IDD 56 mA
Supply Current—Suspended 3 IDD Bus Powered 460 µA
Self Powered 330 µA
Supply Current - USB Pull-up 4 IPU 200 228 µA
Operating Ambient Temperature TA-40 85 °C
Operating Junction Temperature TJ-40 105 °C
Note:
1. All voltages are with respect to VSS.
2. This applies only when using the regulator. When not using the regulator, VREGIN and VDD are tied together externally and it is
allowable for VREGIN to be equal to VDD.
3. If the device is connected to the USB bus, the USB pull-up current should be added to the supply current to calculate total re-
quired current.
4. The USB pull-up supply current values are calculated values based on USB specifications.
CP2108 Data Sheet
Electrical Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 6
3.1.2 UART, GPIO, and Suspend I/O Electrical Characteristics
VDD= 3.0 to 3.6 V, VIO=1.8 V to VDD, VIOHD = 2.7 V to 6.0 V, –40 to +85 °C unless otherwise specified.
Table 3.2. UART, GPIO, and Suspend I/O
Parameter Symbol Test Condition Min Typ Max Unit
Output High Voltage
(All pins except High Drive UART 3
pins 1–6)
VOH VIO – 0.7 V
Output High Voltage
(High Drive UART 3 pins 1–6)
VOH VIOHD
0.7
V
Output Low Voltage
(All pins except High Drive pins 1–
6)
VOL Low Drive
IOL = 3 mA
0.6 V
Output Low Voltage
(High Drive pins 1–6)
VOL High Drive
IOL = 12.5 mA
0.6 V
Input High Voltage VIH 3.0 ≤ VIO ≤ 3.6 VIO – 0.6 V
Input Low Voltage VIL 0.6 V
Weak Pull-up Current
(VIN = 0 V)
IPU VIO = 3.6 V -30 -20 -10 µA
Weak Pull-up Current UART 3
(pins 1–6)
IPU VIOHD = 2.7 V -15 -10 -5 µA
VIOHD = 6.0 V -30 -20 -10 µA
3.1.3 GPIO
–40 to +85°C unless otherwise specified.
Table 3.3. GPIO Output Specifications
Parameter Symbol Test Condition Min Typ Max Unit
RS-485 Active Time After Stop Bit tACTIVE 1 bit time1
TX Toggle Rate fTXTOG 15 Hz
RX Toggle Rate fRXTOG 15 Hz
Clock Output Rate fCLOCK ~158k 20M Hz
Note:
1. Bit-time is calculated as 1 / baud rate.
CP2108 Data Sheet
Electrical Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 7
3.1.4 Reset Electrical Characteristics
–40 to +85 °C unless otherwise specified.
Table 3.4. Reset
Parameter Symbol Test Condition Min Typ Max Unit
Power-On Reset (POR) Threshold VPOR Rising Voltage on VDD 1.4 V
Falling Voltage on VDD 0.8 1 1.3 V
VDD Ramp Time tRMP Time to VDD≥ 3.0 V 10 3000 µs
/RESET Input High Voltage VIHRESET 3.0 ≤ VIO ≤ 3.6 VIO – 0.6 V
/RESET Input Low Voltage VILRESET 0.6 V
/RESET Low Time to Generate a
System Reset
tRSTL 50 ns
3.1.5 Voltage Regulator
–40 to +85 °C unless otherwise specified.
Table 3.5. Voltage Regulator
Parameter Symbol Test Condition Min Typ Max Unit
Output Voltage (at VDD pin) VDDOUT 3.15 3.3 3.4 V
Output Current (at VDD pin)1IDDOUT 150 mA
Output Load Regulation VDDLR 0.1 1 mV/mA
Output Capacitance CVDD 1 10 µF
Note:
1. This is the total current the voltage regulator is capable of providing. Any current consumed by the CP2108 reduces the current
available to external devices powered from VDD.
CP2108 Data Sheet
Electrical Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 8
3.1.6 USB Transceiver
–40 to +85 °C unless otherwise specified.
Table 3.6. USB Transceiver
Parameter Symbol Test Condition Min Typ Max Unit
Valid Supply Range
(for USB Compliance)
VDD 3.0 3.6 V
VBUS Pull-Down Leakage Current IVBUSL VBUS = 5 V, VIO = 3.3 V 10 µA
VBUS Detection Input Threshold VVBUSTH 3.0 ≤ VIO ≤ 3.6 VIO – 0.6 V
Transmitter
Output High Voltage VOH 2.8 V
Output Low Voltage VOL 0.8 V
Output Crossover Point VCRS 1.3 2.0 V
Output Impedance ZDRV Driving High 38 Ω
Driving Low 38 Ω
Pull-up Resistance RPU Full Speed (D+ Pull-up)
Low Speed (D- Pull-up)
1.425 1.5 1.575
Output Rise Time TRLow Speed 75 300 ns
Full Speed 4 20 ns
Output Fall Time TFLow Speed 75 300 ns
Full Speed 4 20 ns
Receiver
Differential Input
Sensitivity
VDI | (D+) - (D-) | 0.2 V
Differential Input Common Mode
Range
VCM 0.8 2.5 V
Input Leakage Current ILPull-ups Disabled <1.0 μA
Refer to the USB Specification for timing diagrams and symbol definitions.
CP2108 Data Sheet
Electrical Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 9
3.2 Absolute Maximum Ratings
Stresses above those listed in 3.2 Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only
and functional operation of the devices at those or any other conditions above those indicated in the operation listings of this specifica-
tion is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. For more information on
the available quality and reliability data, see the Quality and Reliability Monitor Report at http://www.silabs.com/support/quality/pages/
default.aspx.
Table 3.7. Absolute Maximum Ratings
Parameter Symbol Test Condition Min Max Unit
Ambient Temperature Under Bias TBIAS -55 125 °C
Storage Temperature TSTG -65 150 °C
Voltage on VDD VDD VSS – 0.3 4.2 V
Voltage on VREGIN VREGIN VSS – 0.3 6.0 V
Voltage on VBUS VBUS VIO ≥ 3.3 V VSS – 0.3 5.8 V
VIO < 3.3 V VSS – 0.3 VIO + 2.5
Voltage on VIO VIO VSS – 0.3 4.2 V
Voltage on VIOHD VIOHD VSS – 0.3 6.5 V
Voltage on /RESET VIN VIO ≥ 3.3 V VSS – 0.3 5.8 V
VIO < 3.3 V VSS – 0.3 VIO + 2.5 V
Voltage on GPIO or UART pins VIN GPIO/UART pins except 1-6 VSS – 0.3 VIO + 0.3 V
UART pins 1-6 VSSHD
0.3
VIOHD + 0.3 V
Voltage on D+ or D- VIN VIO ≥ 3.3 V VSS – 0.3 5.8 V
VIO < 3.3 V VSS – 0.3 VIO + 2.5 V
Total Current Sunk into Supply Pins ISUPP VDD, VREGIN, VIO,VIOHD 400 mA
Total Current Sourced out of Ground
Pins
IVSS 400 mA
Current Sourced or Sunk by Any I/O
Pin
IPIO UART,GPIO,Suspend I/O, /RESET ex-
cept for UART 3 pins1–6
-100 100 mA
UART 3 pins 1–6 -300 300 mA
Current Injected on Any I/O Pin IINJ UART,GPIO,Suspend I/O, /RESET ex-
cept for UART 3 pins1–6
-100 100 mA
UART 3 pins 1–6 -300 300 mA
Total Injected Current on I/O Pins ∑IINJ Sum of all I/O and /RESET -400 400 mA
Power Dissipation at TA = 85 °C PD 800 mW
Note:
1. VSS and VSSHD provide separate return current paths for device supplies, but are not isolated. They must always be connected to
the same potential on board.
CP2108 Data Sheet
Electrical Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 10
3.3 Thermal Conditions
Table 3.8. Thermal Conditions
Parameter Symbol Test Condition Min Typ Max Unit
Thermal Resistance θJA 25 °C/W
Note:
1. Thermal resistance assumes a multi-layer PCB with any exposed pad soldered to a PCB pad.
3.4 Throughput and Flow Control
The throughput values in the following table are typical values based on bench testing and can serve as a guideline for expected per-
formance. Other factors such as PC system performance and USB bus loading will have an effect on throughput. Each column in the
table shows the typical throughput using 1, 2, 3 or all 4 UART interfaces for the set baud rate.
1. It is not necessary to use hardware flow control if all CP2108 interfaces are configured for 230,400 bps or lower.
2. For baud rates above 230,400 bps, hardware flow control should be used to guarantee reception of all bytes across the UART.
Also, sending data across multiple interfaces simultaneously will cause a reduction in the effective throughput for each interface.
3. UART 3 has lower throughput rates than UARTS 0-2. If the application is configured such that different interfaces will operate at
different baud rates, the interface at the lowest baud rate should be put on UART 3. UART 3 throughput is 5% to 20% slower than
the other interfaces.
4. The performance of UART 3 starts to become significantly slower than the other UART interfaces at baud rates greater than
230,400 bps.
Table 3.9. Throughput Guidelines Comparing UARTS in Operation at Different Set Baud Rates
Set Baud Rate 230,400 (bps) 460,800 (bps) 921,600 (bps) 2M (bps)
1 UART in operation: Throughput 196,900 (bps) 387,200 (bps) 694,200 (bps) 760,000 (bps)
2 UARTs in operation: Throughput 200,400 (bps) 381,600 (bps) 463,700 (bps) 537,400 (bps)
3 UARTs in operation: Throughput 200,300 (bps) 259,800 (bps) 314,800 (bps) 388,000 (bps)
4 UARTs in operation: Throughput 180,300 (bps) 208,900 (bps) 234,000 (bps) 288,200 (bps)
CP2108 Data Sheet
Electrical Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 11
4. Pin Definitions
VSS
58
49
64
63
62
61
60
59
57
56
52
55
54
53
51
50
42
33
48
47
46
45
44
43
41
40
36
39
38
37
35
34
8
1
2
3
4
5
6
7
9
10
14
11
12
13
15
16
24
17
18
19
20
21
22
23
25
26
30
27
28
29
31
32
64 pin QFN
(TopView)
TX0
RX0
RTS0
CTS0
DTR0
DSR0
DCD0
RI0
TX1
VBUS
VSS
VDD
D+
D-
RESET
VREGIN
RTS1
CTS1
DTR1
DSR1
DCD1
RI1
GPIO.0
GPIO.1
VIO
GPIO.3
GPIO.4
GPIO.5
NC
NC
RX1
GPIO.2
VSS
VIO
GPIO.6
GPIO.7
GPIO.13
GPIO.14
GPIO.15
SUSPEND
SUSPEND
DTR2
DSR2
GPIO.8
GPIO.9
GPIO.10
GPIO.11
GPIO.12
RX3
VSSHD
TX3
VIOHD
RTS3
CTS3
TX2
RX2
RTS2
CTS2
DCD2
RI2
DTR3
DSR3
DCD3
RI3
Figure 4.1. CP2108 Pin Definitions
Table 4.1. Pin Definitions for CP2108 QFN64
Pin Name Type Pin Primary Function Alternate Function
VSS Ground 25
59
Device Ground
CP2108 Data Sheet
Pin Definitions
silabs.com | Building a more connected world. Rev. 1.2 | 12
Pin Name Type Pin Primary Function Alternate Function
VSSHD Ground 2 High Drive Device Ground UART 3 pins 1–6.
Connect to Device Ground.
VDD Power (Core) 58 Power Supply Voltage Input
Voltage Regulator Output
VIO Power (I/O)
Non High Drive
24
39
Non High Drive I/O Supply Voltage Input
VIOHD Power (I/O)
High Drive
3 High Drive I/O Supply Voltage Input
VREGIN Power (Regu-
lator)
60 Voltage Regulator Input. This pin is the input to
the on-chip voltage regulator.
RESET Active-low Re-
set
64 Device Reset. Open-drain output of internal POR
or VDD monitor. An external source can initiate a
system reset by driving this pin low for the time
specified in Table 5.
D– USB Data- 63 USB D–
D+ USB Data+ 62 USB D+
VBUS USB Bus
Sense
61 VBUS Sense Input. This pin should be connec-
ted to the VBUS signal of a USB network.
TX0 Digital Output 57 UART 0 Transmit (TX)
RX0 Digital Input 56 UART 0 Receive (RX)
RTS0 Digital Output 55 UART 0 Ready to Send (RTS)
Indicates to the modem that the UART is ready
to receive data.
CTS0 Digital Input 54 UART 0 Clear to Send (CTS)
Indicates the modem is ready to send data to the
UART.
DTR0 Digital Output 53 UART 0 Data Terminal Ready (DTR)
Informs the modem that the UART is ready to es-
tablish a communications link.
DSR0 Digital Input 52 UART 0 Data Set Ready (DSR)
Indicates that the modem is ready to establish
the communications link with the UART.
DCD0 Digital Input 51 UART 0 Data Carrier Detect (DCD)
Indicates that the data carrier has been detected
by the modem.
RI0 Digital Input 50 UART 0 Ring Indicator (RI)
Indicates that a telephone ringing signal has
been detected by the modem.
TX1 Digital Output 49 UART 1 Transmit (TX)
RX1 Digital Input 48 UART 1 Receive (RX)
RTS1 Digital Output 47 UART 1 Ready to Send (RTS)
CTS1 Digital Input 46 UART 1 Clear to Send (CTS)
CP2108 Data Sheet
Pin Definitions
silabs.com | Building a more connected world. Rev. 1.2 | 13
Pin Name Type Pin Primary Function Alternate Function
DTR1 Digital Output 45 UART 1 Data Terminal Ready (DTR)
DSR1 Digital Input 44 UART 1 Data Set Ready (DSR)
DCD1 Digital Input 43 UART 1 Data Carrier Detect (DCD)
RI1 Digital Input 42 UART 1 Ring Indicator (RI)
GPIO.0 Digital I/O 41 General Purpose I/O 0 UART 0 TX Toggle
GPIO.1 Digital I/O 40 General Purpose I/O 1 UART 0 RX Toggle
GPIO.2 Digital I/O 38 General Purpose I/O 2 UART 0 RS-485
GPIO.3 Digital I/O 37 General Purpose I/O 3 Clock Output 0
GPIO.4 Digital I/O 34 General Purpose I/O 4 UART 1 TX Toggle
GPIO.5 Digital I/O 33 General Purpose I/O 5 UART 1 RX Toggle
GPIO.6 Digital I/O 32 General Purpose I/O 6 UART 1 RS-485
GPIO.7 Digital I/O 31 General Purpose I/O 7 Clock Output 1
GPIO.8 Digital I/O 30 General Purpose I/O 8 UART 2 TX Toggle
GPIO.9 Digital I/O 29 General Purpose I/O 9 UART 2 RX Toggle
GPIO.10 Digital I/O 28 General Purpose I/O 10 UART 2 RS-485
GPIO.11 Digital I/O 27 General Purpose I/O 11 Clock Output 2
GPIO.12 Digital I/O 26 General Purpose I/O 12 UART 3 TX Toggle
GPIO.13 Digital I/O 23 General Purpose I/O 13 UART 3 RX Toggle
GPIO.14 Digital I/O 22 General Purpose I/O 14 UART 3 RS-485
GPIO.15 Digital I/O 21 General Purpose I/O 15 Clock Output 3
SUSPEND Digital Output 20 Suspend Indicator - Active High
SUSPEND Digital Output 19 Suspend Indicator - Active Low
DTR2 Digital Output 18 UART 2 Data Terminal Ready (DTR)
DSR2 Digital Input 17 UART 2 Data Set Ready (DSR)
TX2 Digital Output 16 UART 2 Transmit (TX)
RX2 Digital Input 15 UART 2 Receive (RX)
RTS2 Digital Output 14 UART 2 Ready to Send (RTS)
CTS2 Digital Input 13 UART 2 Clear to Send (CTS)
DCD2 Digital Input 12 UART 2 Data Carrier Detect (DCD)
RI2 Digital Input 11 UART 2 Ring Indicator (RI)
DTR3 Digital Output 10 UART 3 Data Terminal Ready (DTR)
DSR3 Digital Input 9 UART 3 Data Set Ready (DSR)
DCD3 Digital Input 8 UART 3 Data Carrier Detect (DCD)
RI3 Digital Input 7 UART 3 Ring Indicator (RI)
RTS3 Digital Output 6 UART 3 Ready to Send (RTS) High Drive
CTS3 Digital Input 5 UART 3 Clear to Send (CTS) High Drive
TX3 Digital Output 4 UART 3 Transmit (TX) High Drive
CP2108 Data Sheet
Pin Definitions
silabs.com | Building a more connected world. Rev. 1.2 | 14
Pin Name Type Pin Primary Function Alternate Function
RX3 Digital Input 1 UART 3 Receive (RX) High Drive
NC No Connect 35
36
CP2108 Data Sheet
Pin Definitions
silabs.com | Building a more connected world. Rev. 1.2 | 15
5. QFN64 Package Specifications
5.1 QFN64 Package Dimensions
Figure 5.1. QFN64 Package Drawing
Table 5.1. QFN64 Package Dimensions
Dimension Min Typ Max
A 0.80 0.85 0.90
A1 0.00 0.02 0.05
b 0.18 0.25 0.30
D 9.00 BSC
D2 3.95 4.10 4.25
e 0.50 BSC
E 9.00 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
CP2108 Data Sheet
QFN64 Package Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 16
Dimension Min Typ Max
Note:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This package outline conforms to JEDEC MO-220.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components.
CP2108 Data Sheet
QFN64 Package Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 17
5.2 QFN64 PCB Land Pattern
Figure 5.2. QFN64 Recommended PCB Land Pattern
Table 5.2. QFN64 PCB Land Pattern Dimensions
Dimension mm
C1 8.90
C2 8.90
E 0.50
X1 0.30
Y1 0.85
X2 4.25
Y2 4.25
CP2108 Data Sheet
QFN64 Package Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 18
Dimension mm
Note:
General
1. All dimensions shown are in millimeters (mm).
2. This Land Pattern Design is based on the IPC-7351 guidelines.
3. All dimensions shown are at Maximum Material Condition (MMC). Least Material Condition (LMC) is calculated based on a Fabri-
cation Allowance of 0.05 mm.
Solder Mask Design
1. 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
1. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release.
2. The stencil thickness should be 0.125 mm (5 mils).
3. The ratio of stencil aperture to land pad size should be 1:1 for all pads.
4. A 3x3 array of 1.0 mm square openings on a 1.5 mm pitch should be used for the center ground pad.
Card Assembly
1. A No-Clean, Type-3 solder paste is recommended.
2. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components.
5.3 QFN64 Package Marking
CP2108-GM
YYWWTTTTTT
e3 TW
Figure 5.3. QFN64 Package Marking
The package marking consists of:
GM – The package type.
TTTTTT – A trace or manufacturing code.
YY – The last two digits of the assembly year.
WW – The two-digit workweek when the device was assembled.
e3 – Lead-free (RoHS compliance) designator.
TW – Device origin (Taiwan) (ISO abbreviation).
CP2108 Data Sheet
QFN64 Package Specifications
silabs.com | Building a more connected world. Rev. 1.2 | 19
6. Typical Connection Diagrams
The CP2108 includes an on-chip 5 to 3.3 V voltage regulator, which allows the CP2108 to be configured as either a USB bus-powered
device or a USB self-powered device. The following figure shows a typical connection diagram of the device in a bus-powered applica-
tion using the regulator. When used, the voltage regulator output appears on the VDD pin and can be used to power external devices.
See 3.1.5 Voltage Regulator for the voltage regulator electrical characteristics.
Note 3
Note 2
Note 1
VBUS
D+
D-
GND
USB
Connector
UART
and GPIO
Signals
CP2108
VREGIN
VDD
VSS
VIO
VBUS
D+
D-
1 µF
1-5 µF 0.1 µF
3.3 V Power
4.7 k
Note 1 : Avalanche transient voltage suppression diodes compatible with Full-speed USB should be added at the
connector for ESD protection. Use Littelfuse p/n SP0503BAHT or equivalent.
Note 2 : An external pull-up is not required, but can be added for noise immunity.
Note 3 : VIO can be connected directly to VDD or to a supply in the range of 3.0-3.6 V.
Note 4: There are 2 VIO pins. All should be connected together. Each pin requires a separate 1 µF and a 0.1 µF
capacitor. VIO can also be connected to VIOHD if VIOHD is in the range of 3.0-3.6 V.
Note 5 : VIOHD can be connected directly to VDD or to a supply in the range of 3.0-6 V.
RX(0-3)
TX(0-3)
RTS(0-3)
CTS(0-3)
DTR(0-3)
DSR(0-3)
RI(0-3)
DCD(0-3)
GPIO.0 – GPIO.15
SUSPEND
VIO
/RESET
/SUSPEND
UART0
UART1
UART2
UART3
Note 4
VSSHD
VIOHD
2.7V-6.0V
0.1 µF
1-5 µF
Note 5
Figure 6.1. Typical Bus-Powered Connection Diagram
CP2108 Data Sheet
Typical Connection Diagrams
silabs.com | Building a more connected world. Rev. 1.2 | 20
There are two configurations for self-powered applications: regulator used and regulator bypassed. To provide VDD in a self-powered
application using the regulator, use the same connections from the previous figure, but connect VREGIN to an on-board 5 V supply and
disconnect it from the VBUS pin. The typical self-powered connections with the regulator used is shown in the following figure.
Note 3
Note 2
Note 1
VBUS
D+
D-
GND
USB
Connector
UART
and GPIO
Signals
CP2108
VREGIN
VDD
VSS
VIO
VBUS
D+
D-
1 µF
1-5 µF 0.1 µF
3.3 V Power
4.7 k
Note 1 : Avalanche transient voltage suppression diodes compatible with Full-speed USB should be added at the
connector for ESD protection. Use Littelfuse p/n SP0503BAHT or equivalent.
Note 2 : An external pull-up is not required, but can be added for noise immunity.
Note 3 : VIO can be connected directly to VDD or to a supply in the range of 3.0-3.6 V.
Note 4: There are 2 VIO pins. All should be connected together. Each pin requires a separate 1 µF and a 0.1 µF
capacitor. VIO can also be connected to VIOHD if VIOHD is in the range of 3.0-3.6 V.
Note 5 : VIOHD can be connected directly to VDD or to a supply in the range of 3.0-6 V.
RX(0-3)
TX(0-3)
RTS(0-3)
CTS(0-3)
DTR(0-3)
DSR(0-3)
RI(0-3)
DCD(0-3)
GPIO.0 – GPIO.15
SUSPEND
VIO
/RESET
/SUSPEND
UART0
UART1
UART2
UART3
Note 4
5 V Power
VIOHD
2.7-6.0 V
0.1 µF
1-5 µF
VSSHD
Note 5
Figure 6.2. Typical Self-Powered (Regulator Used) Connection Diagram
CP2108 Data Sheet
Typical Connection Diagrams
silabs.com | Building a more connected world. Rev. 1.2 | 21
Alternatively, if 3.0 to 3.6 V power is supplied to the VDD pin, the CP2108 can function as a USB self-powered device with the voltage
regulator bypassed. For this configuration, the VREGIN input should be tied to VDD to bypass the voltage regulator. The following fig-
ure shows a typical connection diagram showing the device in a self-powered application with the regulator bypassed.
Note 3
Note 2
Note 1
VBUS
D+
D-
GND
USB
Connector
CP2108
VREGIN
VDD
VSS
VIO
VBUS
D+
D-
1-5 µF 0.1 µF
4.7 k
Note 1 : Avalanche transient voltage suppression diodes compatible with Full-speed USB should be added at the
connector for ESD protection. Use Littelfuse p/n SP0503BAHT or equivalent.
Note 2 : An external pull-up is not required, but can be added for noise immunity.
Note 3 : VIO can be connected directly to VDD or to a supply as low as 1.8 V to set the I/O interface voltage.
Note 4: There are 2 VIO pins. All should be connected together. Each require a separate 1 µF and a 0.1 µF
capacitor.
RXn
TXn
RTSn
CTSn
DTRn
DSRn
RIn
DCDn
GPIO.0 – GPIO.15
SUSPEND
VIO
/RESET
/SUSPEND
3.3 V
Power
VIOHD
2.8V-6.0V
0.1 µF
1-5 µF
UART
and GPIO
Signals
UART0
UART1
UART2
UART3
VSSHD
Note 4
Figure 6.3. Typical Self-Powered Connection Diagram (Regulator Bypass)
CP2108 Data Sheet
Typical Connection Diagrams
silabs.com | Building a more connected world. Rev. 1.2 | 22