In a recent development, a customer faced a challenge in detecting battery voltage using an ADC (Analog-to-Digital Converter) without a dedicated reference input. The battery-powered control circuit required the processor to detect the battery voltage and send out an alert signal when it dropped below a certain level. A proposed solution involved using a 3.3V LDO (Low Drop-Out) regulator, but this approach had several drawbacks, including voltage drop and low voltage issues.
An alternative solution was presented, using a TL431 as a reference voltage to detect the battery voltage. This approach avoided the limitations of the LDO method and ensured accurate detection of the battery voltage. The TL431 regulates the output current as low as 0.5mA, making it suitable for this application.