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 –B–R
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
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 kΩ
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
7. USB Function Controller and Transceiver
The Universal Serial Bus (USB) function controller in the CP2108 is a USB 2.0 compliant full-speed device with integrated transceiver
and on-chip matching and pull-up resistors. The USB function controller manages all data transfers between the USB and the UARTs
as well as command requests generated by the USB host controller and commands for controlling the function of the UARTs and GPIO
pins.
Device pins for UART 0-2 are powered by VIO, while UART 3 pins 1-6 are powered through VIOHD and are high drive pins. These high
drive pins have higher input voltage requirements than other pins which are noted in all the electrical tables.
The USB Suspend and Resume signals are supported for power management of both the CP2108 device as well as external circuitry.
The CP2108 will enter Suspend mode when Suspend signaling is detected on the bus. Upon entering Suspend mode, the CP2108
asserts the SUSPEND and /SUSPEND signals. SUSPEND and /SUSPEND signals are also asserted after a CP2108 reset until device
configuration during USB enumeration is complete.
The CP2108 exits the Suspend mode when any of the following occur: resume signaling is detected or generated, a USB Reset signal
is detected, or a device reset occurs. On exit of Suspend mode, the SUSPEND and /SUSPEND signals are de-asserted. SUSPEND
and /SUSPEND are weakly pulled to VIO in a high impedance state during a CP2108 reset. If this behavior is undesirable, a strong
pulldown (10 kΩ) can be used to ensure /SUSPEND remains low during reset.
The logic level and output mode (push-pull or open-drain) of various pins during USB Suspend is configurable in the EEPROM. See
TODO for more information.
The USB max power and power attributes descriptor must match the device power usage and configuration. See application note
AN721: CP210x/CP211x Device Customization Guide on www.silabs.com/appnotes for information on how to customize USB descrip-
tors for the CP2108.
CP2108 Data Sheet
USB Function Controller and Transceiver
silabs.com | Building a more connected world. Rev. 1.2 | 23
8. Asynchronous Serial Data Bus (UART) Interfaces
The CP2108 contains four UART interfaces, each consisting of the TX (transmit) and RX (receive) data signals and RTS and CTS flow
control signals. The UARTs also support modem flow control (DSR, DTR, DCD, RI).
The UARTs are programmable to support a variety of data formats and baud rates. The Virtual COM Port (VCP) drivers are used to set
the data format and baud rate during COM port configuration on the PC. The data formats and baud rates available to each UART
interface are listed in the following table.
Table 8.1. Data Formats and Baud Rates (All UART Interfaces)
Parameter Value
Data Bits15, 6, 7, 8 (normal mode or fixed mode)
Stop Bits 1, 1.5, 2
Parity Type Odd, Even, Set, Mark, None
Baud Rate 300 bps to 2.0 Mbps1
Note:
1. Review 3.4 Throughput and Flow Control for expected throughput based on selected UART Interface(s) and Baud Rate.
8.1 Baud Rate Generation
The baud rate generator for the interface is very flexible, allowing any baud rate in the range from 300 bps to 2.0 Mbps. If the baud rate
cannot be directly generated from the 80 MHz oscillator, the device will choose the closest possible option. The actual baud rate is
dictated by the following equations.
Clock Divider = 80 MHz
2 × Requested Baud Rate – 1
Actual Baud Rate = 80 MHz
2 × Clock Divider
Most baud rates can be generated with an error of less than 1.0%. A general rule of thumb for the majority of UART applications is to
limit the baud rate error on both the transmitter and the receiver to no more than ±2%. The clock divider value obtained in Equation 1 is
rounded to the nearest integer, which may produce an error source. Another error source will be the 80 MHz oscillator, which is accu-
rate to ±0.25%. Knowing the actual and requested baud rates, the total baud rate error can be found using the following equation.
Baud Rate Error (%) = 100 ×
(
1 – Actual Baud Rate
Requested Baud Rate
)
± 0.25%
The UART interfaces support the transmission and reception of a line break. The CP2108 detects a line break when the RX line is held
low for longer than one byte time at the configured baud rate. The length of a transmitted line break is application-specific: the applica-
tion sends a SET_BREAK command to set the TX line low, and the line stays low until the application sends a CLEAR_BREAK com-
mand.
CP2108 Data Sheet
Asynchronous Serial Data Bus (UART) Interfaces
silabs.com | Building a more connected world. Rev. 1.2 | 24
9. GPIO and UART Pins
The CP2108 supports sixteen user-configurable GPIO pins for status and control information. Each of these GPIO pins are usable as
inputs, open-drain outputs, or push-pull outputs. By default, all of the GPIO pins are configured as a GPIO input. A logic high, open-
drain output pulls the pin to the VIO rail through an internal, pull-up resistor. A logic high, push-pull output directly connects the pin to
the VIO voltage. Open-drain outputs and push-pull outputs are identical when driving a logic low.
The speed to read and write the GPIO pins from an application is subject to the timing of the USB bus. GPIO pins configured as inputs
or outputs are not recommended for real-time signaling.
In addition to the primary GPIO function, each GPIO pin has an alternate function listed in the following table.
More information regarding the configuration and usage of the GPIO pins can be found in application note AN721: CP210x/CP211x
Customization Guide available on the Silicon Labs website: www.silabs.com/appnotes.
Table 9.1. GPIO Mode Alternate Functions
GPIO Pin Alternate Functions
GPIO.0 UART 0 TX Toggle
GPIO.1 UART 0 RX Toggle
GPIO.2 UART 0 RS-485
GPIO.3 Clock Output 0
GPIO.4 UART 1 TX Toggle
GPIO.5 UART 1 RX Toggle
GPIO.6 UART 1 RS-485
GPIO.7 Clock Output 1
GPIO.8 UART 2 TX Toggle
GPIO.9 UART 2 RX Toggle
GPIO.10 UART 2 RS-485
GPIO.11 Clock Output 2
GPIO.12 UART 3 TX Toggle
GPIO.13 UART 3 RX Toggle
GPIO.14 UART 3 RS-485
GPIO.15 Clock Output 3
9.1 GPIO — Alternate Clock Outputs
There are four alternate clock outputs. The clock output frequency is shown in the following equation. Each clock has a 1-byte divider
value. GPIO pins 3,7,11, and 15 can output a configurable CMOS clock output. The clock output appears at the pin at the same time
the device completes enumeration and exits USB Suspend mode. The clock output is removed from the pin when the device enters
USB Suspend mode.
The clocks are derived by dividing the CP2108 core clock, allowing external components to be clocked synchronously with the CP2108.
Clock Output Frequency = 40 MHz
Clock Divider
Note: A clock divider value of 1 is invalid, and a clock divider of 0 results in a frequency of 156 kHz.
CP2108 Data Sheet
GPIO and UART Pins
silabs.com | Building a more connected world. Rev. 1.2 | 25
9.2 GPIO — Transmit and Receive Toggle
GPIO.0, GPIO.1, GPIO.4, GPIO.5, GPIO.8, GPIO.9, GPIO.12, and GPIO.13 pins are configurable as Transmit Toggle and Receive
Toggle pins for the four UART interfaces. These pins are logic high when a device is not transmitting or receiving data, and they toggle
at a fixed rate as specified in 3.1.3 GPIO when data transfer is in progress. Typically, these pins are connected to two LEDs to indicate
data transfer.
CP2108
TX Toggle
RX Toggle
VIO/VIOHD
Figure 9.1. Transmit and Receive Toggle Typical Connection Diagram
CP2108 Data Sheet
GPIO and UART Pins
silabs.com | Building a more connected world. Rev. 1.2 | 26
9.3 RS-485 Transceiver Bus Control
GPIO.2, GPIO.6, GPIO.10, and GPIO.14 are alternatively configurable as RS-485 bus transceiver control pins. When configured for
RS-485 mode, the pin is asserted during UART data transmission and line break transmission. The RS-485 mode is active-high by
default, but the pins can also be configured for active-low mode.
RS-485
Transceiver
R
D
DE
RE
CP2108
TX
RX
RS485
Figure 9.2. RS-485 Transceiver Typical Connection Diagram
CP2108
RS-232
System
TX0
RX0
TX
RX
RTS
CTS
RTS0
CTS0
RS-232
System
TX1
RX1
TX
RX
RTS
CTS
RTS1
CTS1
RS-232
System
TX2
RX2
TX
RX
RTS
CTS
RTS2
CTS2
RS-232
System
TX3
RX3
TX
RX
RTS
CTS
RTS3
CTS3
Figure 9.3. Hardware Flow Control Typical Connection Diagram
CP2108 Data Sheet
GPIO and UART Pins
silabs.com | Building a more connected world. Rev. 1.2 | 27
9.4 Hardware Flow Control (RTS and CTS)
To utilize the functionality of the RTS and CTS pins of the CP2108, each interface must be configured to use hardware flow control.
RTS, or Ready To Send, is an active-low output from the CP2108 and indicates to the external UART device that the CP2108’s UART
RX FIFO has not reached the watermark level of 1536 bytes and is ready to accept more data. When the amount of data in the RX
FIFO reaches the watermark, the CP2108 pulls RTS high to indicate to the external UART device to stop sending data.
CTS, or Clear To Send, is an active-low input to the CP2108 and is used by the external UART device to indicate to the CP2108 when
the external UART device’s RX FIFO is getting full. The CP2108 will not send more than two bytes of data once CTS is pulled high.
The CP2108 stores the received data in internal buffers. It is possible for the CP2108 to receive data on the RX line before a handle to
it is opened. In this case the user may wish to send the data to the USB pipe or may wish to flush it. Similarly, the user may close the
handle while data is still in the internal transmit buffer. It may be desirable to continue sending all of the data out the TX pin after the
handle has been closed. The flush buffer configuration options allow the user to define whether each buffer is flushed when a handle to
the device is opened or closed. By default all the buffers will be flushed when a handle is opened and will not be flushed when a handle
is closed. These options are configurable using Xpress Configurator in Simplicity Studio (www.silabs.com/simplicity) as shown in the
following figure.
Figure 9.4. Flush Buffers Options in Xpress Configurator Customization Utility
CP2108 Data Sheet
GPIO and UART Pins
silabs.com | Building a more connected world. Rev. 1.2 | 28
9.5 High Drive Pins UART 3 Pins 1–6
The UART 3 pins 1–6 are high drive pins that have different input voltage conditions than the other UART and GPIO pins. If an input
voltage for VDD, VIO, and VIOHD is used that is overlapping for the three ranges, then these pins can all be tied together. One of the
benefits of this variation is that UART 3 can accept an input of up to 6 V and therefore can be connected directly to a 5 V device without
additional circuitry.
CP2108 Data Sheet
GPIO and UART Pins
silabs.com | Building a more connected world. Rev. 1.2 | 29
10. Internal EEPROM
The CP2108 includes an internal EEPROM that may be used to customize the USB Vendor ID (VID), Product ID (PID), Product De-
scription String, Power Descriptor, Device Release Number, Interface Strings, and Device Serial Number as desired for OEM applica-
tions. If the EEPROM has not been programmed with OEM data, the default configuration data shown in the following tables are used.
While customization of the USB configuration data is optional, customizing the VID/PID combination is strongly recommended. A
unique VID/PID combination will prevent the driver from conflicting with any other USB driver from a different manufacturer’s product. A
vendor ID can be obtained from www.usb.org, or Silicon Labs can provide a free PID for the OEM product that can be used with the
Silicon Labs VID. Customizing the serial string for each individual device is also recommended if the OEM application is one in which it
is possible for multiple CP210x-based devices to be connected to the same PC. Refer to application note AN721: CP210x/CP211x
Customization Guide for more information about device customization.
Table 10.1. Default USB Configuration Data
Name Description Default Value
Vendor ID (VID) The Vendor ID is a four digit hexadecimal number that is
unique to a particular vendor. 10C4h, for example, is the
Silicon Labs Vendor ID.
10C4h
Product ID (PID) The Product ID is a four digit hexadecimal number that
identifies the vendor's device. EA71h, for example, is the
default Product ID for Silicon Labs' CP2108 USB-to-Quad-
UART Bridge devices.
EA71h
Power Descriptor (Attrib-
utes)
This setting determines whether the device is Bus-Pow-
ered, i.e. it is powered by the host, or Self-Powered, i.e. it
is powered from a supply on the device.
80h (Bus-Powered)
Power Descriptor (Max
Power)
This describes the maximum amount of power that the de-
vice will draw from the host in mA multiplied by 2. For ex-
ample, 32h equates to 100 mA.
32h (100 mA)
Release Number The Release Version is a binary-coded-decimal value that
is assigned by the device manufacturer.
0140h (Release Version 01.4.0)
Serial String The Serial String is an optional string that is used by the
host to distinguish between multiple devices with the same
VID and PID combination. It is limited to 126 characters.
126 characters maximum
Product Description String The Product String is an optional string that describes the
product. It is limited to 126 characters maximum.
"CP2108 USB to Quad Bridge Controller"
(126 characters maximum)
Interface 0 String The Interface String is an optional string that describes
each one of the device's interfaces. Each string is limited
to 43 characters.
"CP2108 Interface 0" (43 characters maxi-
mum)
Interface 1 String The Interface String is an optional string that describes
each one of the device's interfaces. Each string is limited
to 43 characters.
"CP2108 Interface 1" (43 characters maxi-
mum)
Interface 2 String The Interface String is an optional string that describes
each one of the device's interfaces. Each string is limited
to 43 characters.
"CP2108 Interface 2" (43 characters maxi-
mum)
Interface 3 String The Interface String is an optional string that describes
each one of the device's interfaces. Each string is limited
to 43 characters.
"CP2108 Interface 3" (43 characters maxi-
mum)
Table 10.2. Default GPIO, UART, and Suspend Configuration Data
Name Value
GPIO.0 GPIO Input
CP2108 Data Sheet
Internal EEPROM
silabs.com | Building a more connected world. Rev. 1.2 | 30
Name Value
GPIO.1 GPIO Input
GPIO.2 GPIO Input
GPIO.3 GPIO Input
GPIO.4 GPIO Input
GPIO.5 GPIO Input
GPIO.6 GPIO Input
GPIO.7 GPIO Input
GPIO.8 GPIO Input
GPIO.9 GPIO Input
GPIO.10 GPIO Input
GPIO.11 GPIO Input
GPIO.12 GPIO Input
GPIO.13 GPIO Input
GPIO.14 GPIO Input
GPIO.15 GPIO Input
SUSPEND Push-pull, Active-High
SUSPEND Push-pull, Active-Low
RS-485 Level Active-High
The internal EEPROM is programmed using the USB interface. This allows the OEM's USB configuration data and serial number to be
written to the CP2108 on-board during the manufacturing and testing process. A stand-alone utility for programming the internal EE-
PROM is available from Silicon Labs. A library of routines provided in the form of a Windows® DLL is also available. This library can be
used to integrate the EEPROM programming step into custom software used by the OEM to streamline testing and serial number man-
agement during manufacturing. USB descriptors can be locked to prevent future modification.
CP2108 Data Sheet
Internal EEPROM
silabs.com | Building a more connected world. Rev. 1.2 | 31
11. CP2108 Device Drivers
The device driver available for CP2108 is the Virtual COM Port (VCP) driver. The latest drivers are available at www.silabs.com/
vcpdrivers.
11.1 Virtual COM Port (VCP) Drivers
The CP2108 Virtual COM Port (VCP) device drivers allow a CP2108-based device to appear to the PC's application software as four
COM ports. Application software running on the PC accesses the CP2108-based device as it would access four standard hardware
COM ports. However, actual data transfer between the PC and the CP2108 device is performed over the USB interface. Therefore,
existing COM port applications may be used to transfer data via the USB to the CP2108-based device without modifying the applica-
tion. See application note AN197: Serial Communications Guide for the CP210x for example code for interfacing to a CP2108 using the
VCP drivers.
Note: Because the CP2108 uses a USB-based communication interface, timing will not be controllable or guaranteed as it is with a
standard COM port. Full-speed USB operates on 1 ms frames, and the host schedules packets for each USB device where it can in the
1 ms frame. It is recommended to use large data transfers when reading and writing from the host to send data as quickly as possible.
11.2 Driver Customization
In addition to customizing the device as described in 8. Asynchronous Serial Data Bus (UART) Interfaces, the drivers and the drivers
installation package can be also be customized. See application note AN220: USB Driver Customization for more information on gener-
ating customized VCP drivers.
Note: The VID/PID in the drivers must match the VID/PID in the device for the drivers to load properly when the device is connected to
the PC.
11.3 Driver Certification
The default drivers for the CP2108 are Microsoft Windows Hardware Quality Labs (WHQL) certified. The certification means that the
drivers have been tested by Microsoft and their latest operating systems will allow the drivers to be installed without any warnings or
errors.
The customized drivers that are generated using the AN220 software are not automatically certified. To become certified, they must go
first through the Microsoft Driver Reseller submission process. Refer to AN807: Recertifying a Customized Windows HCK Driver Pack-
age for assistance with this process.
CP2108 Data Sheet
CP2108 Device Drivers
silabs.com | Building a more connected world. Rev. 1.2 | 32
12. Relevant Application Notes and Software
The following Application Notes are applicable to the CP2108 devices. The latest versions of these application notes and their accom-
panying software are available at www.silabs.com/interface-appnotes or within Simplicity Studio in the [Application Notes] area.
•AN721: CP210x Device Customization Guide — This application note guides developers through the configuration process of devi-
ces using Simplicity Studio [Xpress Configurator].
•AN197: Serial Communications Guide for the CP210x — This application note describes how to use the standard Windows COM
port function to communicate with the CP210x and includes example code.
•AN220: USB Driver Customization — This application note describes how to use the AN220 software to customize the VCP or
USBXpress drivers with OEM information.
•AN571: CP210x Virtual COM Port Interface — This application note describes the virtual COM port interface and the commands that
can be used with the driver.
•AN807: Recertifying a Customized Windows HCK Driver Package — This document describes the process of recertifying a custom-
ized driver package created by the AN220 driver customization wizard for Windows.
The CP2108 Software Development Kit can be downloaded from www.silabs.com/interface-software. See the Xpress Configurator utili-
ty in Simplicity Studio (www.silabs.com/simplicity) for information on how to customize USB descriptors for the CP2108.
CP2108 Data Sheet
Relevant Application Notes and Software
silabs.com | Building a more connected world. Rev. 1.2 | 33
13. Revision History
13.1 Revision 1.2
February 15th, 2017
Updated orderable part number to CP2108-B03-GM.
Updated 9.1 GPIO — Alternate Clock Outputs and the valid range of clock outputs in 3.1.3 GPIO to match the behavior of the B03
revision devices.
Updated document formatting.
Removed specific operating system versions supported.
Removed the Device Specific Behavior section and moved this information to the device errata.
Merged the Ordering Part Number Information chapter into 1. Feature List and Ordering Information.
Added a note to 11.1 Virtual COM Port (VCP) Drivers regarding data timing with USB.
Added a reference to AN807: Recertifying a Customized Windows HCK Driver Package in 11.3 Driver Certification and 12. Relevant
Application Notes and Software.
Removed a reference to AN335: USB driver Installation Utility from 12. Relevant Application Notes and Software because this software
is no longer utilized by the standard VCP driver package.
Updated 5.3 QFN64 Package Marking to the new format for B03 devices.
13.2 Revision 1.1
February 2014
Added CP2108-B02-GM part number.
Added the Ordering Part Number Information chapter.
Updated URL in 12. Relevant Application Notes and Software.
Added the Device Specific Behavior chapter.
13.3 Revision 1.0
November 2012
Removed preliminary language.
Updated front page feature list.
Added the 2. System Overview chapter.
Updated table formatting in the 3. Electrical Specifications chapter.
Adjusted the order of chapters in the document.
13.4 Revision 0.1
March 2012
Initial release.
CP2108 Data Sheet
Revision History
silabs.com | Building a more connected world. Rev. 1.2 | 34
http://www.silabs.com
Silicon Laboratories Inc.
400 West Cesar Chavez
Austin, TX 78701
USA
Simplicity Studio
One-click access to MCU and
wireless tools, documentation,
software, source code libraries &
more. Available for Windows,
Mac and Linux!
IoT Portfolio
www.silabs.com/IoT
SW/HW
www.silabs.com/simplicity
Quality
www.silabs.com/quality
Support and Community
community.silabs.com
Disclaimer
Silicon Labs intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or
intending to use the Silicon Labs products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical"
parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Labs reserves the right to make changes
without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included
information. Silicon Labs shall have no liability for the consequences of use of the information supplied herein. This document does not imply or express copyright licenses granted
hereunder to design or fabricate any integrated circuits. The products are not designed or authorized to be used within any Life Support System without the specific written consent of
Silicon Labs. A "Life Support System" is any product or system intended to support or sustain life and/or health, which, if it fails, can be reasonably expected to result in significant personal
injury or death. Silicon Labs products are not designed or authorized for military applications. Silicon Labs products shall under no circumstances be used in weapons of mass
destruction including (but not limited to) nuclear, biological or chemical weapons, or missiles capable of delivering such weapons.
Trademark Information
Silicon Laboratories Inc.® , Silicon Laboratories®, Silicon Labs®, SiLabs® and the Silicon Labs logo®, Bluegiga®, Bluegiga Logo®, Clockbuilder®, CMEMS®, DSPLL®, EFM®, EFM32®,
EFR, Ember®, Energy Micro, Energy Micro logo and combinations thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZRadio®, EZRadioPRO®,
Gecko®, ISOmodem®, Precision32®, ProSLIC®, Simplicity Studio®, SiPHY®, Telegesis, the Telegesis Logo®, USBXpress® and others are trademarks or registered trademarks of Silicon
Labs. ARM, CORTEX, Cortex-M3 and THUMB are trademarks or registered trademarks of ARM Holdings. Keil is a registered trademark of ARM Limited. All other products or brand
names mentioned herein are trademarks of their respective holders.
