There is a device on the board. I don't know what it is. It says BU257. It is a 16-pin 8*2 chip. I googled it but still couldn't find any useful information. If anyone knows, please tell me. Thanks.
Dear experts, please help me choose a voltage comparator. Its function is to detect that the voltage at the capacitor end is equal to the reference voltage of the comparator, so that the trigger circu