AST1S31HF Datasheet, PDF (18/33 Pages) STMicroelectronics – Internal soft-start and enable

Functional description
Figure 8. Overcurrent protection region
AST1S31HF
6.5
Enable function
The enable feature allows to put the device into the standby mode. With the EN pin lower
than 0.4 V, the device is disabled and the power consumption is reduced to less than 10 A.
With the EN pin higher than 1.2 V, the device is enabled. If the EN pin is left floating, an
internal pull-down ensures that the voltage at the pin reaches the inhibit threshold and the
device is disabled. The pin is also V_IN compatible.
6.6
Light-load operation
With the peak current mode control loop the output of the error amplifier is proportional to
the load current. The AST1S31HF increases light-load efficiency, when the output of the
error amplifier falls below a certain threshold, the high-side turn-on is prevented.
This mechanism reduces the switching frequency at the light-load in order to save the
switching losses.
6.7
Hysteretic thermal shutdown
The thermal shutdown block generates a signal that turns off the power stage if the junction
temperature goes above 150 °C. Once the junction temperature goes back to about 130 °C,
the device restarts into the normal operation.
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DocID026968 Rev 2