Have you ever experienced a MAX232 or MAX3232 heating or burning? Many engineers in the process of single-chip microcomputer program development, unknown reason in the use of RS232 chip found burned, spent a lot of effort also do not understand the reason. To solve this problem, just follow these guidelines.
Follow manufacturer’s data book
Machine development engineers say the MAX232 / MAX3232 is produced by many different companies. Each company has its own specifications and attributes. So first of all, you need to refer to different manufacturers. For example:
MAX232 – Texas Instruments;
MAX232 – American letter;
St232 – Italian semiconductor;
Ic232 – Reza;
Sp232a – aikejia;
ADM232A – ADI；
Hin232 – Riza;
MAX3232 – Texas Instruments;
MAX3232 – Mercure;
St3232 – Italian semiconductor.
I see two common mistakes that people make.
1、 Connection between charge pump and capacitor
Just check the IC data book of Texas Instruments (TI) and MAX232. You will find that for Texas Instruments (TI) IC, you can connect charge pump capacitor C3 to GND or VCC.
But for Mercure, we need to connect it to the VCC itself. Therefore, if your IC is grounded in your IC, it may be damaged. Therefore, it is better to connect capacitor C3 to VCC (5V) to make it compatible with Texas Instruments (TI) and Meixin chips.
About the capacity of capacitor?
MCU engineers said that different IC need to use different capacitor (C1, C2, C3, C4) values. In particular, if you are using the MAX3232, refer to the specific data book and select the capacitor value. If the MAX232 chip is used, a 1pf ceramic capacitor can be used because it is compatible with Texas Instruments (TI) and Mercure.
2、 Unused input pins are grounded
All of these IC drivers have one input channel and one output channel. If you refer to ICS produced by different companies above, you will find that all inputs of some ICs have internal pull-up or pull-down resistors, but they are usually not suitable for chips commonly used in the market. As a result, if the input pin is hanging, there may be pickup noise and high voltage due to oscillation.
At present, there are many low-quality chips on the market. Usually, the same supplier will provide cheap and high quality products of the same kind. Therefore, it is recommended to purchase chips from well-known suppliers and ask them to provide high-quality chips.