L7983 datasheet(18/43 Pages) STMICROELECTRONICS

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If the EN pin is forced lower than VENL the switching activity is stopped. The L7983 can further reduce the input

current as soon as EN is forced lower than the VWAKEUPL threshold. When this occurs the input current is reduced

to ISHTDWN = 2.3 µA (typ.).

Figure 15. Turn-off example

A divider from VIN can be used to program the input voltage threshold for controlled power-up, as shown in

Figure 16.

The EN pin is VIN compatible.

Figure 16. Input voltage turn-on threshold programming

VIN

EN/UVLO

FSW

VCC

VOUT(FB)

VBIAS

RST

LNM/LCM

GND

During the soft-start, the L7983 is not allowed to sink current from the output, also if LNM operation is selected.

This feature is intended to guarantee the proper power-up also in case of output voltage pre-bias condition.

Following the L7983 turn-on, if the output voltage (sensed through the VOUT(FB) pin) is detected higher than the

VRSTTHR threshold, the RST pin is left floating.

During the operation, the RST pin is asserted low if the output voltage is found lower than the VRSTTHR -

VRSTHYST threshold, i.e. a typical 2% hysteresis is implemented.

L7983

Enable and Reset

DS13354 - Rev 1

page 18/43

L7983 数据表(PDF) 18 Page - STMicroelectronics