L9654 datasheet(26/59 Pages) STMICROELECTRONICS

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Functional description

L9654

26/59

DocID14218 Rev 3

4.10.1

Deployment driver diagnostic

L9654 is able to perform a short to battery, a short to ground, a resistance measurement

and a MOS diagnostics on its deployment drivers. A short to ground and an open circuit

conditions are distinguished using a resistance measurement. Here below is shown the

diagram of deployment driver diagnostic.

The diagnostic is performed when a valid SPI command is received. Each current source

(ISRC and IBIAS) and current sink (ISINK, IPD_SQH) is turned on or off by an SPI command.

IPD_SQH is turned on when IBIAS is turned on. This pull-down (IPD_SQH) is used to deplete

the charge left on the SQH and SQL capacitors. IPD is permanently connected to SQL. This

current sink pulls down SQL pin during an open circuit condition.

Diagnostic current source or sink and comparator or amplifier are independent. It is possible

to turn on or off the current source or sink on a specific channel, while monitoring the

comparator or amplifier on a different channel. This feature is used to run a short between

loop diagnostic.

Figure 13. Deployment driver diagnostic diagram

4.10.2

Continuity diagnostic

A continuity diagnostic includes a short to battery, a short to ground and an open circuit

diagnostic.

During a continuity diagnostic, IBIAS is switched on. On a normal loading condition, SQH

voltage is below SBTH threshold and SQL voltage is above SGTH threshold.

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