Answer: The CH340G is WCH’s full-speed USB to UART bridge in SOP-16. It needs an external 12 MHz crystal with two 33 pF capacitors, and in return it has the tightest TX baud error in the CH340 family (<0.3 %) and the wider −40 to 85 °C rating. It runs from 5 V (V3 decoupled with 0.1 µF) or 3.3 V (V3 tied to VCC), and brings out all six modem lines. (WCH CH340DS1 V3D, pp.2–10.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Package | SOP-16, 3.9 mm body, 1.27 mm pitch | — | §3, p.2 |
| Supply, 5 V mode | 4.0 / 5 / 5.3 V | V3 to 0.1 µF only | §6.2, p.8 |
| Supply, 3.3 V mode | 2.9 / 3.3 / 3.6 V | V3 tied to VCC | §6.3, p.9 |
| Operating current | 7 typ / 20 max mA (5 V); 4 typ / 12 max mA (3.3 V) | TA 25 °C | §6.2–6.3, pp.8–9 |
| USB suspend current | 0.09 typ / 0.2 max mA (5 V); 0.08 / 0.2 mA (3.3 V) | — | §6.2–6.3 |
| Clock input (XI) | 11.98 / 12.00 / 12.02 MHz | External crystal or clock | §6.4, p.9 |
| Crystal load capacitors | 33 pF each (ceramic resonator: maker’s value, usually 47 pF) | — | §7.1, p.10 |
| TX baud-rate error | < 0.3 % | Receive tolerance about 2 % | §5.4, p.7 |
| Baud rates | 50 bps – 2 Mbps (listed standard rates) | — | §2 p.1; §5.4 p.7 |
| Input levels, 5 V | VIL ≤ 0.9 V; VIH ≥ 2.3 V | VCC 5 V | §6.2, p.8 |
| Input levels, 3.3 V | VIL ≤ 0.8 V; VIH ≥ 1.9 V | VCC 3.3 V | §6.3, p.9 |
| Ambient temperature | −40 to 85 °C | Operating | §6.1, p.8 |
| Absolute max VCC / pin voltage | −0.5 to 6.0 V / −0.5 V to VCC + 0.5 V | — | §6.1, p.8 |
Pinout (SOP-16)
| Pin | Name | Type | Notes (WCH pin table, pp.3–4) |
|---|---|---|---|
| 1 | GND | Power | USB ground |
| 2 | TXD | Out | Idles high |
| 3 | RXD | In | Built-in pull-up/down; keep high when idle |
| 4 | V3 | Power | 5 V: 0.1 µF to GND · 3.3 V: tie to VCC |
| 5 / 6 | UD+ / UD− | USB | Connect directly; no series resistors (pull-up is internal) |
| 7 / 8 | XI / XO | Clock | 12 MHz crystal + 2 × 33 pF |
| 9–12 | CTS#, DSR#, RI#, DCD# | In | Modem inputs, active low |
| 13 | DTR# | Out | Also a configuration input before enumeration (see below) |
| 14 | RTS# | Out | Modem output, active low |
| 15 | R232 | In | High = invert RXD for the simple RS232 circuit; built-in pull-down |
| 16 | VCC | Power | 0.1 µF decoupling |
Supply wiring
- 5 V (USB powered): VBUS → VCC, with 0.1 µF on V3 and 0.1 µF on VCC. The inputs then accept 0 to 0.9 V as low and 2.3 V up to VCC as high. A 3.3 V MCU’s TX (≥ 2.3 V high) can drive RXD directly, but CH340G’s TXD swings to about 5 V.
- 3.3 V: tie V3 to VCC and feed 3.3 V. WCH notes that every circuit connected to the chip must then stay at or below 3.3 V (§5.1, p.5).
- Separate supplies for CH340 and MCU can back-feed current through the I/O pins. WCH shows diode-and-NMOS protection (§7.7) and says it generally does not recommend powering the two separately.
Crystal layout
Place the 12 MHz crystal and its two 33 pF caps close to pins 7–8 and surround them with ground copper (§7.1). If a low-cost ceramic resonator won’t start, WCH suggests halving the capacitor on XI.
DTR# at power-up
Before USB configuration completes, DTR# (pin 13) is read as a configuration input. A 4.7 kΩ pull-down to GND makes the chip request a larger supply current in its USB descriptor (§5.1, p.5). Keep reset circuits on DTR# from pulling it low at plug-in unless that is what you want.
Pitfalls specific to CH340G
- Adding series resistors on D+/D−. WCH says to wire UD+/UD− straight to the bus, because the transceiver and pull-up are internal (§3 note, §5.1).
- Tying R232 (pin 15) high without meaning to. A high level inverts RXD for the simplified RS232 circuit. The pin has a built-in pull-down, so leave it open for TTL use; the chip reads it only once after power-on reset (§5.1).
- Copying 22 pF from old notes. The V3D datasheet specifies 33 pF for a quartz crystal.
- Dropping in CH340C to save the crystal without checking the temperature range (−20 to 70 °C) and pin 8 (OUT#). See the CH340C page.
Part numbers (information only)
CH340G (SOP-16). Sister parts in the same datasheet: CH340C and CH340B (SOP-16, no crystal), CH340E (MSOP-10), CH340N (SOP-8), CH340K (ESSOP-10), CH340X (MSOP-10), CH340T (SSOP-20). WCH lists no packing suffix for CH340G.
FAQ
- Does CH340G need a crystal? Yes: a 12 MHz crystal with two 33 pF capacitors on pins 7 and 8.
- Can CH340G run from 3.3 V? Yes, from 2.9 to 3.6 V with V3 tied to VCC.
- What is the maximum baud rate of CH340G? 2 Mbps. For one-way rates of 1 Mbps or more, WCH recommends CH343.
- Do I need resistors on D+ and D−? No. WCH says to connect UD+ and UD− directly.
- What temperature range is CH340G rated for? −40 to 85 °C ambient.
Related (internal links)
- CH340 selector
- CH340G alternatives: CH340C, CH340E, CP2102, FT232RL
- WCH CH340C
- WCH CH340E
- USB-UART bridges
Sources (retrieved 2026-10-26)
- WCH, USB to Serial Port chip CH340 Datasheet (CH340DS1), Version 3D: PDF https://www.wch-ic.com/download/file?id=79 ; download page https://www.wch-ic.com/downloads/CH340DS1_PDF.html (page numbers are the printed page footers).
Disclaimer
Values are copied from WCH CH340DS1 Version 3D, read on 26 Oct 2026; electrical values are at TA 25 °C. Verify against the current datasheet and test on your hardware.
Reviewed by: Jasper · Updated: 2026-10-26