CH343P from WCH Jiangsu Qin Heng, in a TQFN-16-EP(3x3). Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	VIO	power_in	I/O port power supply input for UART and RST pins. Supports 1.8V-5.5V; should share the supply used by the connected MCU. Requires an external decoupling capacitor. Not fed by V3/VDD5 internally and no reverse current path.
2	GND	power_in	Common ground. Must be connected to the USB bus ground. Pin 0 (exposed pad on the underside of the QFN) is also GND and is optional but recommended for connection.
3	VDD5	power_in	Positive supply input to the internal 3.3V LDO regulator. Accepts 4.0-5.5V when V3 is not tied to VDD5, or 3.0-3.6V when V3 is tied to VDD5. Requires an external decoupling capacitor.
4	TXD	output	UART serial data output. Idle state is high. Referenced to VIO.
5	RXD	input	UART serial data input with an internal pull-up to VIO (typ. ~60 uA at 3.3V). Idle state is high.
6	V3	power_in	Internal 3.3V LDO regulator output and core/USB PHY supply input. When VDD5 < 3.6V, tie V3 to VDD5 and feed 3.3V externally; when VDD5 > 3.6V, leave V3 with only its decoupling capacitor (0.1 uF). LDO drive capability ~10 mA.
7	UD+	bidirectional	USB D+ data line. Connect directly to the USB bus D+; no series resistor allowed (internal USB transceiver/1.5K pull-up per USB 2.0 full-speed).
8	UD-	bidirectional	USB D- data line. Connect directly to the USB bus D-; no series resistor allowed.
9	VBUS	input	USB bus VBUS presence detection input with internal pull-down (controllable via MCR OUT1 to close/open the pull-down). Also supports the VIO low-voltage protection scheme when a series resistor + external PMOS is used to switch VIO. Abs max 6.5V.
10	ACT#	output	USB enumeration/configuration-complete status output, active low. Inactive during USB suspend. Typically used to drive an LED (through a series resistor to VIO) or notify the MCU that the USB link is up.
11	DCD	input	MODEM handshake input: Data Carrier Detect, active low. Driven by the peer's DCE.
12	DTR/TNOW	output	Default: MODEM DTR output, active low. If a ~4.7 kOhm pull-down is detected on this pin at power-up/reset, the pin auto-switches to TNOW (transmit-in-progress indicator, active high) for driving RS485 DE/RE# in half-duplex mode.
13	RTS	output	MODEM handshake output: Request To Send, active low. Also used by the hardware auto-flow-control logic (asserted while the RX buffer has room).
14	DSR	input	MODEM handshake input: Data Set Ready, active low. Internal pull-up to VIO.
15	CTS	input	MODEM handshake input: Clear To Send, active low. Used by the auto-flow-control logic to gate transmission. Internal pull-up to VIO.
16	RI	input	MODEM handshake input: Ring Indicator, active low. Internal pull-up to VIO.
0	GND	power_in	Exposed thermal/ground pad on the underside of the QFN16 package. Connection is optional but recommended; ties to the same net as pin 2 GND.

Key specifications

Parameter	Value
Manufacturer	WCH Jiangsu Qin Heng
Package	TQFN-16-EP(3x3)
Category	Interface
Pins	17

Ordering variants

Same part, different packaging or reel option.

CH343P
CH343G
CH343C
CH343K

CAD (KiCad official)

Symbol: CH343P
Footprint: Package_DFN_QFN:QFN-16-1EP_3x3mm_P0.5mm_EP1.7x1.7mm
3D model: TQFN-16-EP(3x3) (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`ch343p.step`	190 KB	You want the bare part, or you mark your own boards.
`ch343p-etched.step`	1.4 MB	You want the part with `CH343P` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 366 faces against 110 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: WCH Jiangsu Qin Heng datasheet (8 pp, sha256 656a3a7bd49d78a4, retrieved 2026-08-17, tier: lcsc)
Datasheet language: Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF