The TS831 ultra low power integrated circuit incorporates a high stability band-gap voltage reference and a comparator with open drain output. The threshold voltage is set at 4.33V for TS831-5, 4.5V for TS831-4 and 2.71V for TS831-3 by internal thermally matched resistances. The comparator exhibits a 20s response (with 10mV overdrive) and has an open drain output active when input voltage is lower than the threshold. An internal hysteresis, 100mV for TS831-4/ TS831-5 and 60mV for TS831-3, increases the comparator's noise margin and prevents false reset operation.