VNF1248F datasheet(23/79 Pages) STMICROELECTRONICS

23 / 79 page

Figure 8. VDS monitor self-test flow sequence

_THRS

Ext FET VDS Monitor

Self-test configuration

VDS Monitor

Self-test

Configuration

CR#1→ S_T_CFG = -1-

CR#2→ VDS

= <user option>

SELF-TEST CONFIGURATION

Turn-on pull-down current generator to produce

additional voltage offset of 100mV on VDS Monitor

inputs

A/D CONVERSIONS & DELTA MEASURES

Perform VDS SAR A/D conversions

Compute difference between self-test measures and

last user measure available in Status Register SR#4

Store data result, selftest status and fault emulation

check in Status Register SR#5

UNLOCKED STATE

SELF-TEST STATE

Ext FET VDS Monitor

Self-test

Execution

Ext FET VDS Monitor

Self-test

END

UNLOCKED STATE

S_T_START = 1

LOCKED

S_T_STOP = 1

WD Timeout

HWLO = 1

TS_T_ACTIVE time duration

00 = IDLE

01 = RUN

10 = END

11 = ABORT

SELF-TEST CLOSURE

Turn-off pull-down current generator to restore

normal voltage drop on VDS Monitor inputs

No VDS A/D conversions during this timeframe

Parity

Status

ADC self-test result

S_T_VDS_MAX1

TS_T_WAIT time duration

During TS_T_ACTIVE and TS_T_WAIT

timeframes, VDS protection

is inhibited, whilst all

other protections are

active

(Self-test aborted,

state transition

after TS_T_WAIT

expiration)

(Self-test aborted, state

transition after TS_T_WAIT

expiration)

TEST COMPLETED

TS_T_ACTIVE = 5us

TS_T_WAIT = 5us

4.3

External FET stuck-on self-test

The goal of this self-test is to verify the proper turn-off of the external power switch, by monitoring its VDS behavior

in time.

Starting from the unlocked State, the external FET stuck-on self-test is activated through a dedicated SPI frame

(CR#1, S_T_START and S_T_CFG fields).

At execution start the external FET is automatically turned-off, regardless of its status during previous operations,

then continuous AtoD conversions of VDS voltage, sensed across external power switch terminals, are performed

in order to allow the user to monitor VDS evolution in time.

VNF1248F

Self-test

DS14109 - Rev 7

page 23/79

VNF1248F Datasheet(PDF) 23 Page - STMicroelectronics

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