L9396 datasheet(70/109 Pages) STMICROELECTRONICS

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System functional safety implementations

L9396

70/109

DS12539 Rev 6

6 V ≤ VBST ≤ 19 V; -40 °C ≤ Tj ≤ 175 °C unless otherwise noted.

7.3

Fault output

The device provides a digital push-pull output. In its default configuration, the output is

controlled low when the watchdogs are properly served and controlled high in case of

watchdog errors. The meaning of watchdog error for WD1 is different in interrupt mode

respect to warning lamp mode. In the first case it will be considered as a fault an event that

causes a WD COUNTER decrease, while in the second case, the fault considered is a WD1

reset (so the most critical fault for WD1). About WD2 error, all faults will be considered,

generating a reset.

This output can be used as a pre-driver for a passive warning lamp using the proper SPI Bit.

With a proper SPI configuration, FAULT output pin can act as an interrupt signal to the µC in

case of:



status change on wake-up input (IGN),



over / under-voltage detections (see table below),



thermal warnings (see table below).

Feedbacks can be programmed as mask-able via SPI register ADV_CONFIG (see

Table 51).

In case of the above faulty conditions, with FAULT output configured in Interrupt mode, the

FAULT output is driven high for tFAULT_ACT in case of IGN status change and Watchdogs

errors, while it is driven high for other faults (OT and over/under voltage detections) until the

faults disappear and tFAULT_ACT expires.

In case of faulty conditions, with FAULT output configured as passive warning lamp driver,

the output is driven high until the faults disappear and the related flags are read.

FAULT output is enabled (exit of high impedance state) only at the end of power up cycle.

This happens only when undervoltage of regulators (VPREREG, VCC, VCC5, VCORE) is

no more present after power up.

Table 50. Oscillator electrical characteristics

Symbol

Parameter

Test condition

Min

Typ

Max

Unit

fOSCINT

Internal Oscillator main

frequency

15.1

16.9

MHz

fOSCINT_mod_freq

Spread spectrum

modulation frequency

Guaranteed by

scan

-125

kHz

fOSCINT_mod_id_min

Spread spectrum minimum

modulation index

--5

-2

fOSCINT_mod_id_max

Spread spectrum maximum

modulation index

-2

fOSCINT2

Internal second oscillator

frequency

-1.7

2.3

MHz

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