CH3330N – Small and Cheap USB-Serial Converter IC Needs No Crystal

CH3330N – Small and Cheap USB-Serial Converter IC Needs No Crystal

Recently the hobbyist market has seen the appearance of the Air602 low-cost ARM WiFi module. This module might be a potential competitor of ESP8266, another low-cost powerful WiFi module, that took the electronics hobbyists by storm long ago and is still extremely popular. But what’s more interesting about the Air602 module is the usage of a completely new USB to Serial Chip – WCH CH330N. This chip has features similar to CH340, but fewer pins (e.g. DTS, and  CTS are missing), and available in a tiny SOP8 package.


Here is a brief explanation about USB to Serial chip and what is its usage. A USB to Serial converter converts USB (Universal Serial Bus) signal to UART (Universal Asynchronous Receiver Transmitter) signal and vice-versa. Most 8-bit and 16-bit low-cost microcontrollers do not feature built-in USB stack, rather they have UART peripheral. So, in order to establish communication between a PC that features USB and a microcontroller that only has UART, a converter is used.

UART Signal - Captured using logic analyzer
UART Signal – Captured using a logic analyzer


USB Signal - Captured using logic analyzer
USB Signal – Captured using a logic analyzer

CH330N is catching the attention of tinkerers for its small 8-pin-only form factor, built-in crystal oscillator, and compatibility with CH340 drivers. The CH340 (or CH340G) is yet another USB to Serial converter IC that has been popular for a long period of time. It has a higher pin count compared to CH330N and also supports CTS and DTS, but requires external oscillator circuitry in order to work. The CH330N, on the other hand, is way cheaper than the CH340 and requires only a few external components. This USB to Serial converter supports baud rate from 50 bps to 2 Mbps. The following schematic diagram shows the application of CH330,

CH330 Schematics
CH330 Schematics

This little fellow costs only $0.3535 when order quantity is within 10 pieces, but if you purchase more than 120 pieces, it becomes $0.2829 only. You can purchase from LCSC – a China-based electronics components seller and my personal favorite for their wide range of products, lower price range, and very low shipping charge. The datasheet is in Chinese and can be found here.

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Myself Rik and I am founder of Riktronics. I study Electronics and Communication Engineering in IIE. My hobby is playing with electronics and making various projects, mainly about embedded systems. Love to do coding, and making tutorials about electronics/programming. Contact me in any need at a[email protected] My blog :

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