L9779WD datasheet(75/170 Pages) STMICROELECTRONICS

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L9779WD

Functional description

169

6.12.1

External MOSFET gate pre-drivers diagnosis

Each channel locally detects and writes its own fault or no-fault condition (codified on 2 bit

according to the Table 28: Fault encoding condition).



Short circuit to battery or overcurrent for all the outputs during ON condition.



Open load or short to GND during OFF condition.

The faults are latched and reset at every Read Diag operation.

In “off” conditions the first fault detected is latched and can be overwritten only by the ON

condition fault.

Channel “on”

Short to Vb:

Current diagnosis is the result of a comparison between Drain pin voltage and the internal

Vshort threshold selected by MSC.

If: Vdrain> Vshort for t > TSHORT

the driver is switched off and the fault is set, latched and reset at every Read Diag

operation.

When the fault occurs the driver is switched off with a controlled slew-rate.

The drivers switches on AGAIN in the following conditions:

–

If command goes LOW and than HIGH again

–

If command remains active driver is switched automatically on at every Read Diag

operation.

Short to GND:

Not available.

Open load:

Not available.

DRAIN8_9,

OUT8_9

Tshort

Short to VB fault filter time.

Programmable from 1.3 µs to

170 µs, Test by scan

--25%

1.3

+25%

µs

2.6

5.2

(defaul

170

1. 0.172 for OUT8.

Table 30. External MOSFET gate pre-drivers (continued)

Symbol

Parameter

Test condition

Min

Typ

Max

Uni

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