Manufacturer: WCH (Jiangsu Qinheng)
Figures from the datasheet: WCH (Jiangsu Qinheng) CH340DS1, rev. 3D
USB to UART serial bridge in SOP-16 with modem signals and an external 12 MHz crystal, common on low-cost Arduino-compatible and ESP8266 boards.
The CH340G is a full-speed USB 2.0 to serial bridge from WCH. It provides TXD/RXD plus the modem signals RTS#, DTR#, CTS#, DSR#, RI# and DCD#, supports baud rates from 50 bps to 2 Mbps and runs from either 5 V or 3.3 V. Unlike the CH340C/N/K/E/X/B, it needs an external 12 MHz crystal. On a computer it uses WCH's CH341 VCP driver. Board makers usually drive an auto-reset circuit from DTR# and RTS#. The figures on this page come from the WCH CH340 datasheet, version 3D.
Interactive package pinout and pin mapping for SOP-16.
Package illustration, not a dimensioned mechanical drawing.
| # | Pin name | Type | 5V Tolerant | Alternate functions / details |
|---|---|---|---|---|
| GND | ground | — | Common ground, connected directly to the USB ground | |
| TXD | digital io | No | Serial data output (transmit); idle high | |
| RXD | digital io | No | Serial data input (receive) with built-in controllable pull-up and pull-down; idle high | |
| V3 | power in | — | Internal 3.3 V node: 0.1 µF to GND when VCC is 5 V; tie to VCC when VCC is 3.3 V | |
| UD+ | digital io | No | USB D+; connect directly to the USB bus without a series resistor (pull-up is internal) | |
| UD- | digital io | No | USB D−; connect directly to the USB bus without a series resistor | |
| XI | analog in | No | Crystal oscillator input: 12 MHz crystal with load capacitor to GND | |
| XO | analog out | — | Crystal oscillator output: 12 MHz crystal with load capacitor to GND | |
| CTS# | digital io | No | Clear To Send modem input, active low (internal pull-up not stated in the datasheet) | |
| DSR# | digital io | No | Data Set Ready modem input, active low (internal pull-up not stated in the datasheet) | |
| RI# | digital io | No | Ring Indicator modem input, active low (internal pull-up not stated in the datasheet) | |
| DCD# | digital io | No | Data Carrier Detect modem input, active low (internal pull-up not stated in the datasheet) | |
| DTR# | digital io | No | Data Terminal Ready modem output, active low; often drives the MCU auto-reset. Before USB configuration it is read as an input (4.7 kΩ pull-down requests a larger supply current) | |
| RTS# | digital io | No | Request To Send modem output, active low; often drives the boot/reset circuit | |
| R232 | digital io | No | Auxiliary RS232 enable, active high, built-in pull-down; leave unconnected for a TTL UART | |
| VCC | power in | — | Supply: 4.0–5.3 V (5 V mode) or 2.9–3.6 V with V3 tied to VCC; 0.1 µF decoupling capacitor |
| Parameter | Min | Typical | Max | Unit | Test condition |
|---|---|---|---|---|---|
| Supply Voltage, 5 V Mode(VCC_5V) | 4 | 5 | 5.3 | V | V3 connected only to a 0.1 µF capacitor |
| Supply Voltage, 3.3 V Mode(VCC_3V3) | 2.9 | 3.3 | 3.6 | V | V3 tied to VCC (CH340G) |
| Pin Voltage(VIO) | -0.5 | — | VCC + 0.5 | V | Absolute maximum; I/O is not 5 V tolerant at 3.3 V |
| Supply Current(ICC) | — | 7 | 20 | mA | VCC = 5 V, operating (4 / 12 mA at 3.3 V) |
| Suspend Current(ISLP) | — | 0.09 | 0.2 | mA | USB suspended, VCC = 5 V |
| Baud Rate(Baud) | — | 50 bps – 2 Mbps | — | bps | Standard rates up to 2 000 000 |
| Transmit Baud Rate Error(BaudErr) | — | < 0.3 | — | % | CH340G with a 12 MHz crystal; receive tolerance about 2 % |
| USB Interface(USB) | — | 2.0 Full-Speed | — | USB | — |
| Crystal Frequency(f_osc) | 11.98 | 12 | 12.02 | MHz | 33 pF load capacitors (47 pF for a ceramic resonator) |
| Power-On Reset Threshold(VR) | 2.4 | 2.6 | 2.8 | V | — |
| Max supply voltage (VDD/VCC) | 6 V |
| Operating junction temperature | -40 – 85 °C |
| Storage temperature | -55 – 125 °C |
Real-world hardware caveats, PCB layout constraints and silicon errata to know before manufacturing.
Pin 4 (V3) is wired differently in the two supply modes. At 5 V, V3 gets only a 0.1 µF capacitor to GND and must not be connected to VCC. At 3.3 V, V3 is tied to VCC, and nothing connected to the chip may exceed 3.3 V.
The USB transceiver and the D+ pull-up are internal. WCH recommends connecting UD+ and UD− straight to the USB lines without extra resistors.
If the CH340G runs from USB VBUS while the MCU has its own supply, current flows through TXD/RXD into whichever side is unpowered. The CH340G pins are not protected against this (unlike CH340K, CH340X and later CH340C/N lots).
The CH340G needs a 12 MHz quartz crystal between XI and XO with 33 pF capacitors to GND; a ceramic resonator usually needs about 47 pF. If the oscillator is hard to start, WCH suggests halving the XI capacitor.
| Part number (MPN) | Manufacturer | Compatibility | Electrical differences / BOM considerations |
|---|---|---|---|
| CH340C | WCH | pin to pin drop in | Built-in clock: omit the crystal and its capacitors; pin 7 must be left unconnected and pin 8 becomes OUT#. Operating range −20…70 °C; transmit baud error below 1.8 %. |
| CP2102 | Silicon Labs | functional requires bom change | Different package (QFN-28) and pinout, with its own driver; see the Silicon Labs datasheet. |
This component is physically fitted to the following reference development boards in CircuitBase:
Primary semiconductor vendor datasheets, errata, and application notes.
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