ST1S10 step-down regulator – can I drive the EN pin from the voltage divider

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The ST1S10 step-down regulator ( has an INHibit (active low) / ENable (high) input terminal, like any other DC-DC regulator I guess.

I'd like to use it for an UVLO function. I initially thought of matching a voltage divider in a way that my battery cut-off voltage is at the high-low transition level of the EN pin of ST1S10. In the datasheet I can see though that the Vmax for OFF is 0.4V and Vmin for ON is 1.2.

What happens between 0.4V – 1.2V? Is that the hysteresis that I can rely on or is that an unknown state?

Best Answer

0.4V and 1.2V are just the guaranteed limits. The typical threshold is around 0.75V, but it is strongly temperature dependent (see figure 12 in the datasheet).

You need an external comparator and voltage reference. Depending on the input voltage range and detection threshold required, a voltage supervisor IC might do the job (eg. TC54VC). However you may find that the regulator turns back on when the load is removed and battery voltage 'bounces back', in which case you will need a circuit with more hysteresis or a lockout function.