L9963T-TR datasheet(31/45 Pages) STMICROELECTRONICS

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3.5.2

Main oscillator monitor

The oscillator used for the main logic functionalities and digital timings is monitored with a redundant oscillator

that is electrically independent from the main one. Redundant oscillator is used just for safety purpose, in order to

check a possible drift condition.

In case a failure is detected, communication is inhibited in both directions since ISOline and SPI blocks are kept

disabled. If fault disappears, the device becomes fully functional again and any BNE Short Detection is reset,

thus re-engaging the BNE output.

Table 26. Main oscillator electrical parameters

Symbol

Parameters

Test conditions

Min

Typ

Max

Unit

FAUX_OSC

Internal redundant Oscillator frequency

MHz

Freq_diff

Oscillator drift detection threshold

Guaranteed by design

+/-12

+/-22

3.5.3

BNE short detection

A short to GND/VDD detection is implemented to protect the BNE output buffer. If the value forced on the BNE

output buffer differs from the one sampled by the CPOL input buffer for more than TBNE_SHORT_DET, the BNE

output buffer is put into HiZ.

Automatic re-engagement of the BNE output buffer occurs upon next Stand-by state to Normal state transition

(MCU needs to toggle DIS pin).

3.5.4

SPICLKFREQ Comparator BIST

The analog comparators used for latching SPICLKFREQ value are BISTed during Trimming & Config Latch.

In case the BIST fails, the slowest SCLK configuration is chosen (250 kHz).

MCU is supposed to implement a communication timeout mechanism able to detect slower than normal

communication bit rate.

L9963T

Safety and diagnostic features

DS13590 - Rev 4

page 31/45

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