L9678P datasheet(33/203 Pages) STMICROELECTRONICS

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L9678P, L9678P-S

Start-up power control

202

4.3.6

VSUP linear regulator (optional)

The VSUP linear regulator can be used to provide 7 V derived directly from battery line with

an external power transistor. This voltage rail can be used mainly to supply PSI-5 remote

sensor interface. The stability of the regulation loop is guaranteed by use of a small external

capacitor. Current limitation is provided by means of controlling output current on BVSUP

pin. The external pass transistor gives the flexibility to easily address different current loads.

The VSUP regulator is enabled in the ACTIVE mode and continues operation in the

PASSIVE mode using power from energy reserve. In the case of L9678P (no remote sensor

interfaces), VSUP can be externally connected to ground.

Figure 16. VSUP control behavior

4.3.7

VSF linear regulator

The fully integrated VSF linear regulator provides a 20V voltage nominal (configurable to

25V via SPI command) derived directly from ERBOOST. This voltage rail is used in case an

external n-ch safing FET has to be used. The stability of the regulation loop is guaranteed

by use of a small external capacitor. Current limitation is implemented. A minimum drop-out

of 2V between ERBOOST and VSF is needed. VSF is enabled by the assertion of any

ARMxINT signal, or by the assertion of (FENH and not (FENL)), as shown in Figure 17

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