CH340G USB to serial IC: specs and pinout
The WCH CH340G, a USB to serial UART bridge chip in a 16-pin SOP/SOIC package. It needs an external 12 MHz crystal and capacitors. Sold here as a bare chip, so board-level facts (USB connector, regulator) do not apply.
Specs
| Spec | Value | Source |
|---|---|---|
| Interface | USB 2.0 full-speed device to asynchronous serial; 50 bps to 2 Mbps; hardware full duplex | source Section 2 Features |
| Supply, 5 V mode | VCC 4.0 V to 5.3 V (V3 pin only to a capacitor, not to VCC); typ 5 V | source Section 6.2 5V Electrical Parameters |
| Supply, 3.3 V mode | VCC 2.9 V to 3.6 V for CH340G, with V3 connected to VCC; typ 3.3 V | source Section 6.3 3.3V Electrical Parameters |
| Operating current, 5 V | 7 mA typ, 20 mA max (CH340G/C/N/K/E/X/T/R) | source Section 6.2 |
| Operating current, 3.3 V | 4 mA typ, 12 mA max | source Section 6.3 |
| USB suspend current | 0.09 mA typ, 0.2 mA max at 5 V; 0.08 mA typ, 0.2 mA max at 3.3 V (CH340G) | source Sections 6.2 and 6.3 |
| Input levels, 5 V supply | VIL 0 to 0.9 V; VIH 2.3 V to VCC | source Section 6.2 |
| Input levels, 3.3 V supply | VIL 0 to 0.8 V; VIH 1.9 V to VCC | source Section 6.3 |
| Output levels, 5 V supply | VOL max 0.5 V at 6 mA sink; VOH min VCC-0.6 V at 2 mA | source Section 6.2 |
| Absolute maximum supply and temperature | VCC -0.5 V to 6.0 V; pin voltage -0.5 V to VCC+0.5 V; operating -40 C to 85 C (CH340G/T/R) | source Section 6.1 |
| Crystal | 12 MHz crystal and oscillation capacitors required for CH340G (the C/N/K/E/X/B variants have a built-in clock) | source Sections 3 and 4 |
Power
| Value | Source | |
|---|---|---|
| Supply | VCC 4.0 to 5.3 V (5 V mode) or 2.9 to 3.6 V (3.3 V mode, V3 tied to VCC) | source Sections 6.2, 6.3 |
| Current | 7 mA typ at 5 V; 4 mA typ at 3.3 V (chip only) | source Sections 6.2, 6.3 |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
This is a bare chip; pin numbers are the SOP-16 column of the maker's pin table. No module or board is covered.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| 16 VCC | Positive power input; 0.1 uF decoupling; with 3.3 V supply connect V3 to VCC | source Section 4 Pin table, SOP16 column | ||
| 1 GND | Common ground, to USB ground | 0 V | source Section 4 Pin table, SOP16 column | |
| 4 V3 | With 3.3 V supply connect to VCC; with 5 V supply connect a 0.1 uF decoupling capacitor | source Section 4 Pin table, SOP16 column | ||
| 7 XI | CH340G: crystal oscillator input, needs external 12 MHz crystal and capacitors | source Section 4 Pin table, SOP16 column | ||
| 8 XO | CH340G: crystal oscillator output | source Section 4 Pin table, SOP16 column | ||
| 5 UD+ | Connect directly to the D+ line of USB, no series resistor | source Section 4 Pin table, SOP16 column | ||
| 6 UD- | Connect directly to the D- line of USB, no series resistor | source Section 4 Pin table, SOP16 column | ||
| 2 TXD | Serial data output | source Section 4 Pin table, SOP16 column | ||
| 3 RXD | Serial data input, built-in controllable pull-up and pull-down | source Section 4 Pin table, SOP16 column | ||
| 9 CTS# | MODEM input, active low | source Section 4 Pin table, SOP16 column | ||
| 10 DSR# | MODEM input, active low | source Section 4 Pin table, SOP16 column | ||
| 11 RI# | MODEM input, active low | source Section 4 Pin table, SOP16 column | ||
| 12 DCD# | MODEM input, active low | source Section 4 Pin table, SOP16 column | ||
| 13 DTR# | MODEM output, active low | source Section 4 Pin table, SOP16 column | ||
| 14 RTS# | MODEM output, active low | source Section 4 Pin table, SOP16 column | ||
| 15 R232 | Auxiliary RS232 enable, active high, built-in pull-down | source Section 4 Pin table, SOP16 column |
Build with it
Project ideas for the CH340G USB to serial IC. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Replace the USB chip on a Nano clone: Only for a board whose USB chip is marked CH340G; the maker lists the C variant as a different, clockless chip. Disconnect USB and all power before any rework, work with ventilation (hot air and flux fumes) and ESD care, and read the chip marking on the board first: many Nano clones use a CH340C (built-in clock), which is a different chip from the CH340G. Learning project in SMD rework.
- Replace the USB chip on an Uno clone: The board must already use a CH340G with its own crystal and capacitors, which stay on the board; check the marking. Orientation of pin 1 matters. Disconnect USB and all power before any rework, work with ventilation (hot air and flux fumes) and ESD care, and read the chip marking on the board first: many Nano clones use a CH340C (built-in clock), which is a different chip from the CH340G. Learning project.
- A serial loopback test for a repaired Uno R3 CH340G board using jumper wires and a serial monitor: With the ATmega held in reset, joining the TX and RX header pins sends the chip's own output back to its input, so typed characters echo if the chip works. Read the chip marking first; this test is for a CH340G board. Learning project.
Common mistakes
- The CH340G needs an external 12 MHz crystal; the built-in-clock variants are CH340C, N, K, E, X and B, which are different chips (source: link, Sections 3 and 4).
- In 3.3 V mode V3 must be tied to VCC; in 5 V mode V3 gets only a 0.1 uF capacitor to ground, never the supply (source: link, Section 4).
- Pin numbers differ by package: on the CH340G (SOP-16) pin 16 is VCC and pin 1 is GND, unlike the SSOP-20 numbering (source: link, Section 4).
Not covered by the official source
- Pin numbers are the SOP-16 column of the maker's pin table; the maker's PDF is the reference for any board layout.
- The title says RS232; the chip gives TTL-level serial and RS232 needs an extra level-conversion part per the maker's sheet.
Sources
- link (WCH CH340 Datasheet Version 3D)