In portable devices, we often use simple resistive voltage divider circuits to monitor battery voltage. This circuit is extremely low-cost and straightforward to design. However, it has a critical flaw—even after the device powers down, these two resistors still form a loop, continuously draining battery power. For devices pursuing extreme low power consumption and extended standby time, this leakage current ranging from microamps to tens of microamps is an absolutely unacceptable waste. So, how can we completely resolve this issue and achieve true ‘zero shutdown power consumption’? Today, we'll start with the simplest circuit and step-by-step optimize it into three solutions.