L9396 datasheet(27/109 Pages) STMICROELECTRONICS

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DS12539 Rev 10

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L9396

Power supply

109

3.7

VCORE regulator

This regulator provides the supply to the µC core. The flexible approach with the external

voltage divider allows the rail to be regulated from 0.8 V to 5 V. It can also be configured

either as a buck controller or as a linear controller, driving an external FET in both cases.

Figure 5. VCORE configuration diagram (buck regulator - top, linear regulator -

bottom)

Typically 2.2 Ω resistor has to be inserted between GCORE pin and gate of the external

FET for buck configuration. For buck configuration, the source of the external FET should be

connected to the SCORE pin, and the output tank capacitor should be connected to the

VCORE pin. For linear configuration, the output tank capacitor should be connected with the

source of the external FET and the SCORE pin, while VCORE pin should be either tied to

ground or shorted to SCORE.

The operating mode (Linear, Buck) is selected when the regulator is enabled; mode

recognition assumes that VCORE capacitance is fully discharged at each power-up. Some

residual VCORE voltage, lower than 2.6 V, is allowed as reported in the relevant Application

Note AN5702.

The mode selected for VCORE operation can be read via SPI in SUPPLY_CONTROL_1

Note:

When linear mode is selected for VCORE, in order to guarantee the right functionality it is

recommended to tie VCORE to GND or eventually realize the short between SCORE and

VCORE at device pin level, minimizing the parasitic path coming from the PCB routing.

The VCORE regulator has over and under voltage detections and the VCORE is not shut

down in case of over or under voltage. It is also protected against short to ground by

monitoring regulation loop for VCORE buck or over current for VCORE linear. When short to

ground is detected and lasts more than the filter time of tflt_oc_vcore, the vcore is shut down

Buck

Configuration

VCOREFDBK

GCORE

SCORE

VCORE

CBS

Linear

configuration

VCOREFDBK

GCORE

SCORE

VCORE

GADG1901171138PS

I_CORE_SL

I_CORE_SH

I_CORE_SL

I_CORE_SH

(w/ Stop Mode bypass

with ext. FET

LDO)

Volt. Mon.

22uH

VPREREG

L9396

68k

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