L5965 datasheet(19/73 Pages) STMICROELECTRONICS

19 / 73 page

Figure 9. Pre regulator BUCK1

PGND1

GL1

Sensen/p

COMP1

VREG

BST1

VBAT1

GH1

PH1

Rsense

VBUCK1

GAPG2206151644PS

In dropout operation the external high-side MOSFET is kept always on; every fourth clock cycle it has to be turned

off for 180ns to recharge bootstrap capacitor. This allows a maximum duty cycle of 98%.

BUCK1 controller provides the following diagnostic:

•

Monitor of the output voltage is monitored by an independent circuit for UV/OV detection: thresholds are

set via SPI.

•

Monitor of the Power Good thresholds: are set via SPI (at 5/10% of VBUCK1) and the status is provided via

SPI bit.

•

Over Current Protection via current sense amplifier.

•

Over Temperature detection by a local thermal sensor.

•

PGND1 loss detection.

If BUCK1 is set as Main BUCK pre-regulator:

•

If a UV/OV fault occurs, then Fault pin is asserted and the corresponding fault bit is set inside the SPI

possible to enable or disable the reset for all regulators together by OTP. The reset moves the device to

REC state.

•

If OT occurs, the power stage is switched OFF with a 16 µs filter time. The output decreases until UV is

detected. The regulator goes in REC state and can restart only when OT flag is reset. The corresponding

SPI bit is set and FAULT pin is asserted.

•

The over current limitation is a cycle by cycle protection: when the fault happens, the corresponding fault

bit (Buck_OC_STAT) is set in the SPI register. This bit doesn't change the regulator behavior. If the fault

happens for 7 consequent cycles, the FAULT pin is asserted (latched).

•

If PGND1 ground loss occurs, all regulators are turned OFF, FAULT and RESET_B pins are asserted and

device goes back to REC state. Until the fault is present, any tentative of turning on the regulator is

ignored.

If BUCK1 is set as BUCK post-regulator we have the same behavior as above, except that:

L5965

Voltage regulators and features description

DS12567 - Rev 3

page 19/73

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