Answer: The CH340C is the SOP-16 CH340 with a built-in clock, so no crystal or load capacitors. The trade-offs: TX baud error is <1.8 % (vs <0.3 % for CH340G), the internal clock drifts up to ±1.8 % from −25 to 75 °C, the part is rated −20 to 70 °C, and pin 8 is OUT#, a modem output, where CH340G has XO. It keeps DTR# on pin 13, so Arduino-style auto-reset still works. (WCH CH340DS1 V3D, pp.2–9.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Package | SOP-16, 3.9 mm body, 1.27 mm pitch | — | §3, p.2 |
| Clock | Internal; no crystal or capacitors | — | §3 note p.2; §5.1 p.5 |
| Internal clock error | ±1.2 % max (−5 to 55 °C); ±1.8 % max (−25 to 75 °C) | Typ ±0.8 % / ±1.0 % | §6.4, p.9 |
| TX baud-rate error | < 1.8 % | Receive tolerance about 2 % | §5.4, p.7 |
| Supply, 5 V mode | 4.0 / 5 / 5.3 V; 7 typ / 20 max mA | V3 to 0.1 µF | §6.2, p.8 |
| Supply, 3.3 V mode | 3.1 / 3.3 / 3.6 V; 4 typ / 12 max mA | V3 tied to VCC | §6.3, p.9 |
| USB suspend current | 0.05 typ / 0.15 max mA (5 V); 0.04 / 0.15 mA (3.3 V) | — | §6.2–6.3 |
| Ambient temperature | −20 to 70 °C | Operating | §6.1, p.8 |
| Pin 7 / pin 8 | NC (leave unconnected) / OUT# (modem output, active low) | — | Pin table, p.3 |
| Power-on reset | Threshold 2.4 / 2.6 / 2.8 V; time 20 / 35 / 50 ms | — | §6.2 p.8; §6.4 p.9 |
| Baud rates | 50 bps – 2 Mbps (listed standard rates) | — | §5.4, p.7 |
Pinout differences from CH340G
All pins are the same as on CH340G except two:
| Pin | CH340G | CH340C |
|---|---|---|
| 7 | XI | NC: WCH says it must be left unconnected |
| 8 | XO | OUT#: software-defined modem output, active low |
So a CH340G board can take a CH340C only if the crystal and both capacitors are removed (or never fitted). With them in place, pin 8 drives into a capacitor and a crystal.
Is the internal clock good enough?
The receiver on each end tolerates roughly 2 % total mismatch (WCH quotes about 2 % for CH340’s receiver). CH340C uses up to 1.8 % of that by itself at the edges of its range:
| Far-end MCU error | CH340C worst case | Sum | vs ~2 % |
|---|---|---|---|
| 0.1 % (crystal MCU) | 1.8 % | 1.9 % | Marginal pass |
| 0.5 % | 1.8 % | 2.3 % | Fails the screen |
| 0.5 %, room only (−5 to 55 °C, 1.2 %) | 1.2 % | 1.7 % | Pass |
This is a screening estimate; check your MCU’s own receive tolerance.
Lot-dependent features
WCH ties two features to the lot number printed on the chip:
- 5 V-tolerant I/O / no back-feed: CH340C with a lot number starting with 4 blocks current flowing into the I/O pins when the CH340C is unpowered (§5.1 p.5; §7.7 p.14).
- Second DTR# on pin 8: only on lots starting with 4 whose last three characters are above B40. A 4.7 kΩ pull-down on pin 8 switches it to an open-drain DTR# for the BOOT pin of an MCU (§5.3 p.7; §7.9).
Neither is guaranteed for other lots, so check the marking before relying on them.
Pitfalls specific to CH340C
- Leaving the CH340G crystal parts in place. Pin 8 is OUT#, not XO.
- Using it outdoors or in a car. It is rated −20 to 70 °C only.
- Running long links at high baud with an RC-clocked MCU. The two clock errors add up.
- Budgeting 3.3 V operation from 2.9 V. CH340C needs at least 3.1 V; only G/T/R go down to 2.9 V.
Part numbers (information only)
CH340C (SOP-16). WCH lists no packing suffix. The lot number on the package decides the optional features above.
FAQ
- Is CH340C a drop-in replacement for CH340G? Same footprint, but remove the crystal and caps; pin 8 becomes OUT#, and the rating drops to −20 to 70 °C.
- Does CH340C have DTR for Arduino auto-reset? Yes, on pin 13, the same as CH340G.
- How accurate is the CH340C internal clock? ±1.2 % from −5 to 55 °C and ±1.8 % from −25 to 75 °C (max).
- What is pin 7 on CH340C? NC; WCH says leave it unconnected.
- What minimum voltage does CH340C need at 3.3 V? 3.1 V, with V3 tied to VCC.
Related (internal links)
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. Lot-dependent features are as WCH describes them; we have not tested them on hardware. Baud screening is an estimate.
Reviewed by: Jasper · Updated: 2026-10-26