Part: CH9102F — WCH

Type: USB to Asynchronous Serial Port Converter

Description: The CH9102 is a USB bus adapter chip that implements USB to asynchronous serial port conversion, compatible with USB V2.0 full-speed, supporting communication baud rates from 50bps to 4Mbps, and offering flexible I/O voltage options for the serial port.

Operating Conditions:

• Supply voltage (USB side): 3.3V or 5V
• Serial port I/O voltage (CH9102F): 1.8V, 2.5V, 3.3V, 5V
• Communication baud rate: 50bps to 4Mbps

Key Specs:

• USB compatibility: Full-speed USB V2.0
• Baud rate range: 50bps to 4Mbps
• Data bits: 5, 6, 7, or 8 bits
• Parity options: Odd, even, space, mark, no parity
• Flow control: CTS and RTS hardware automatic flow control
• Serial port I/O voltage (CH9102F): 1.8V, 2.5V, 3.3V, 5V
• Built-in features: Power-on reset, clock, EEPROM (CH9102F)

Features:

• Full-speed USB device interface, compatible with USB V2.0
• Built-in firmware, emulates standard serial port
• Fully compatible with serial port applications under Windows operating system
• Supports driver-free operating system built-in CDC class driver or multi-functional high-speed VCP vendor driver
• Hardware full-duplex serial port, built-in independent transmit and receive buffers
• Supports common MODEM handshake signals RTS, DTR, DCD, RI, DSR, CTS
• Supports CTS and RTS hardware automatic flow control
• Supports half-duplex, provides TNOW status for RS485 switching during transmission
• Supports RS232 interface through external level shifting devices
• USB side supports 5V and 3.3V power supply voltages
• CH9102F serial port I/O independently powered, supports 5V, 3.3V, 2.5V, 1.8V power supply voltages, supports anti-backflow
• CH9102X serial port I/O supports 3.3V signals, supports anti-backflow
• Built-in power-on reset, built-in clock, no external crystal oscillator required
• CH9102F has built-in EEPROM, configurable chip VID, PID, maximum current value, manufacturer and product information strings, and other parameters
• Chip has built-in Unique ID (USB Serial Number)

Applications:

• Expanding asynchronous serial ports for computers
• Upgrading ordinary serial devices or MCUs to the USB bus

Package:

• QFN24 (4x4mm)
• QFN28X5 (5x5mm)

• Full-speed USB device interface, compatible with USB V2.0
• Built-in firmware, emulates standard serial port, used for upgrading original serial peripherals, or adding extra serial ports via USB
• Fully compatible with serial port applications under Windows operating system on the computer side, no modification required
• Supports driver-free operating system built-in CDC class driver or multi-functional high-speed VCP vendor driver
• Hardware full-duplex serial port, built-in independent transmit and receive buffers, supports communication baud rates from 50bps to 4Mbps
• Serial port supports 5, 6, 7 or 8 data bits, supports odd parity, even parity, space, mark, and no parity
• Supports common MODEM handshake signals RTS, DTR, DCD, RI, DSR, CTS
• Supports CTS and RTS hardware automatic flow control
• Supports half-duplex, provides TNOW status for RS485 switching during transmission
• Supports RS232 interface through external level shifting devices
• USB side supports 5V and 3.3V power supply voltages
• CH9102F serial port I/O independently powered, supports 5V, 3.3V, 2.5V, 1.8V power supply voltages, supports anti-backflow
• CH9102X serial port I/O supports 3.3V signals, supports anti-backflow
• Built-in power-on reset, built-in clock, no external crystal oscillator required
• CH9102F has built-in EEPROM, configurable chip VID, PID, maximum current value, manufacturer and product information strings, and other parameters
• Chip has built-in Unique ID (USB Serial Number)
• Provides QFN24 and QFN28 lead-free packages, RoHS compliant

V1.4 1

CH9102 Manual https://wch.cn

CH9102F Pinout

Package: QFN-24-EP (4×4mm, 0.5mm pitch)

Pin Number	Pin Name	Type	Description
1	RI	I/O	Ring Indicator
2	GND	P	Ground
3	UD-	I/O	USB Data Minus
4	UD+	I/O	USB Data Plus
5	GND	P	Ground
6	V3	P	3.3V Power Supply
7	VDD5	P	5V Power Supply
8	RST#	I	Reset (Active Low)
9	ACT#	O	Activity Indicator (Active Low)
10	VBUS	I	USB VBUS
11	WAKEUP/GPIO3	I/O	Wakeup / GPIO3
12	TNOW/GPIO2	I/O	Timeout / GPIO2
13	GND	P	Ground
14	NC	—	No Connect
15	GND	P	Ground
16	CTS	I	Clear to Send
17	SUSPEND/GPIO1	I/O	Suspend / GPIO1
18	CTS	I	Clear to Send
19	RTS	O	Request to Send
20	RXD	I	Receive Data
21	TXD	O	Transmit Data
22	DSR	I	Data Set Ready
23	DTR	O	Data Terminal Ready
24	DCD	I	Data Carrier Detect
0 (EP)	GND	P	Exposed Pad / Ground (optional but recommended)

Notes

• Pin 0 (Exposed Pad): The bottom thermal/exposed pad is GND and is optional but recommended for connection; all other GND pins (2, 5, 13, 15) are necessary connections.
• USB Pins (UD+/UD-): Cannot be connected in series with resistors; direct connection required per USB 2.0 specification.
• GPIO Pins: Pins 11, 12, and 17 have alternate GPIO functions (GPIO3, GPIO2, GPIO1 respectively).
• Pin 14: No Connect pin.

Name	Parameter Description	Parameter Description	Parameter Description	Min	Typ	Max	Unit
VDD5	USB V3 pin not connected to VDD5, V3 connected to capacitor	USB V3 pin not connected to VDD5, V3 connected to capacitor	USB V3 pin not connected to VDD5, V3 connected to capacitor	4.0	5	5.5	V
VDD5	Power supply voltage V3 pin connected to VDD5, VDD5=V3	Power supply voltage V3 pin connected to VDD5, VDD5=V3	Power supply voltage V3 pin connected to VDD5, VDD5=V3	3.0	3.3	3.6	V
VIO	VIO power supply voltage for serial port and other I/O	VIO power supply voltage for serial port and other I/O	VIO power supply voltage for serial port and other I/O	1.7	5	5.5	V
IVDD	VDD5 or V3 power supply current during operation	VDD5 or V3 power supply current during operation	VDD5 or V3 power supply current during operation		3	15	mA
IVIO	VIO power supply current during operation (depends on I/O load)	VIO power supply current during operation (depends on I/O load)	VIO power supply current during operation (depends on I/O load)		0	(10)	mA
ISLP	USB VDD5 power supply = 5V	USB VDD5 power supply = 5V	USB VDD5 power supply = 5V		0.09	0.16	mA
ISLP	During suspend	VDD5=V3 power supply = 3.3V	VDD5=V3 power supply = 3.3V		0.085	0.15	mA
ISLP	Power supply current	VIO power supply, no I/O load/pull-up	VIO power supply, no I/O load/pull-up		0.002	0.05	mA
ILDO	Internal power regulator external load capability	Internal power regulator external load capability	Internal power regulator external load capability			10	mA
VIL			VIO=5V	0		1.5	V
VIL	Low-level input voltage	Low-level input voltage	VIO=3.3V	0		0.9	V
VIL			VIO=1.8V	0		0.5	V
VIH			VIO=5V	2.5		VIO	V
VIH	High-level input voltage	High-level input voltage	VIO=3.3V	1.9		VIO	V
VIH			VIO=1.8V	1.3		VIO	V
VIHVBS	VBUS pin high-level voltage	VBUS pin high-level voltage	VIO=1.8V~5V	1.7		5.8	V
VOL		VIO=5V, sinking 15mA current	VIO=5V, sinking 15mA current		0.4	0.5	V
VOL	Low-level	VIO=3.3V, sinking 8mA current	VIO=3.3V, sinking 8mA current		0.3	0.4	V
VOL	Output voltage	VIO=1.8V, sinking 3mA current	VIO=1.8V, sinking 3mA current		0.3	0.4	V
VOH	High-level	VIO=5V, sourcing 10mA current	VIO=5V, sourcing 10mA current	VIO-0.5	VIO-0.4		V
VOH	Output voltage	VIO=3.3V, sourcing 5mA current	VIO=3.3V, sourcing 5mA current	VIO-0.4	VIO-0.3		V
VOH	Non-reset state	VIO=1.8V, sourcing 2mA current	VIO=1.8V, sourcing 2mA current	VIO-0.4	VIO-0.3		V
IPUP	Serial port and RST pins	Serial port and RST pins	VIO=5V	35	150	220	μA
IPUP	Pull-up current	Pull-up current	VIO=3.3V	15	60	90	μA
IPUP	(Pull-up to VIO voltage)	(Pull-up to VIO voltage)	VIO=1.8V	3	14	21	μA
IPDN			VBUS>1.6V	6	10	16	μA
IPDN	VBUS pin pull-down current	VBUS pin pull-down current	VBUS<1.3V	50	140	200	μA
VRV3	V3 power-on reset/low-voltage reset voltage threshold	V3 power-on reset/low-voltage reset voltage threshold	V3 power-on reset/low-voltage reset voltage threshold	2.5	2.7	2.9	V
VRVIO	VIO power low-voltage reset voltage threshold	VIO power low-voltage reset voltage threshold	VIO power low-voltage reset voltage threshold	0.8	1.0	1.15	V
VESD	HBM ESD withstand voltage on USB or I/O pins	HBM ESD withstand voltage on USB or I/O pins	HBM ESD withstand voltage on USB or I/O pins	5	6		KV

Note: Dimensions are in mm (millimeters).

Pin center spacing is a nominal value with no error. Other dimensions have a tolerance of no more than ±0.2mm.

Order Model	Package Type
CH9102F	QFN24
CH9102X	QFN28X5