AST1S31HF datasheet(18/33 Pages) STMICROELECTRONICS

18 / 33 page

Functional description

AST1S31HF

18/33

DocID026968 Rev 2

Figure 8. Overcurrent protection region

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 VIN 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.

AST1S31HF Datasheet(PDF) 18 Page - STMicroelectronics