This undervoltage, protection circuit uses one comparator with a precision, integrated reference to create an alert signal at the comparator output (OUT) if the battery voltage sags below 2.0 V. The undervoltage alert in this implementation is ACTIVE LOW. So when the battery voltage drops below 2.0 V, the comparator output goes low, providing as an alert signal to whatever device is monitoring the output. Hysteresis is integrated in the comparator such that the comparator output will return to a logic high state when the battery voltage rises above 2.034 V. This circuit utilizes an open-drain output comparator in order to level shift the output high logic level for controlling a digital logic input pin. For applications needing to drive the gate of a MOSFET switch, a comparator with a push-pull output is preferred.
- Battery voltage levels (V_bat)
- Undervoltage (V_low) < 2.00 V
- Start-up operating voltage (V_high) > 2.034 V
- Comparator output status (OUT)
- Low battery: V_OL < 0.4 V
- Normal operation: V_OH = V_PU = 1.8 V