VNF1048F datasheet(22/52 Pages) STMICROELECTRONICS

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Protections

5.1

Battery undervoltage shutdown

The device is able to operate down to Vs = 6 V, with the charge pump still active. If the battery supply voltage

Vs falls below the undervoltage shutdown threshold, the device enters in Battery undervoltage mode. The current

sense diagnostic is not available. The charge pump, the output stage and the bypass switch are off regardless of

the SPI status.

If VS rises above the threshold (VS_USD + VS_USD_hys) the device returns to the last mode.

An undervoltage flag is set in the SPI register when VS < VS_USD, and automatically reset when

VS>VS_USD+VS_USD_hys.

5.2

Device overtemperature shutdown

The device temperature is internally monitored. An overtemperature shut-down of the device occurs when TJ

exceeds TTSD. The charge pump, the output stage and the bypass switch are off. A fault indication is given via

SPI.

The device restarts when TJ decreased below TTSD - TTSD_HYS.

VTJ is converted by a dedicated ADC converter. The converted result is stored in the Status register and can be

read via SPI.

5.3

External MOSFET overtemperature shutdown

The external MOSFET temperature is monitored through a 10 kΩ NTC thermistor with one terminal connected to

the Drain of the MOSFET, in order to allow optimal component placement.

RNTC is part of a VBG (1.2 V) voltage divider through NTC and NTC_M pins:

VNTC= VBG×RNTC

RT_REF+RNTC

(1)

VNTC is converted by a dedicated ADC converter. The converted result is stored in the Status register and can be

read via SPI.

An overtemperature shut-down of the MOSFET occurs when VNTC voltage decreases under a preset threshold.

The threshold can be set via SPI in the range from 100 °C to 150 °C in steps of 5 °C. In this case both output

stages and bypass switch are turned off.

The MOSFET and the bypass switch are re-armed via SPI by clearing latched fault NTC_OVT bit.

This protection is not active in case of external MOSFET in OFF state.

5.4

External MOSFET desaturation shut-down

The external MOSFET drain-source voltage is monitored by the Control IC. A desaturation shut-down of the

MOSFET occurs when the VDS exceeds the preset threshold. In this case both output stage and bypass switch

are turned off. The threshold can be set via SPI in the range 0.3 V to 1.80 V in steps of 50 mV (default = 300 mV).

The MOSFET and bypass switch are re-armed via SPI by clearing latched fault VDS_MAX bit.

VDS is converted by a dedicated ADC converter. The converted result is stored in the Status register and can be

read via SPI.

This protection is not active in case of external MOSFET in OFF state.

VNF1048F

Protections

DS13084 - Rev 6

page 22/52

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