L99DZ120 datasheet(87/162 Pages) STMICROELECTRONICS

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L99DZ120

Application information

161

Figure 37. H-bridge GSHx slope

4.25

Resistive low

The resistive output mode protects the devices and the H-bridge in the standby mode and in

some failure modes (thermal shutdown TSD1 (SR 1), charge pump low CP_LOW (SR 2)

and DI pin stuck at ‘1’ SPI_INV_CMD (SR 2)). When a gate driver changes into the resistive

output mode due to a failure a sequence is started. In this sequence the concerning driver is

switched into sink condition for 32 μs to 64 μs to ensure a fast switch-off of the H-bridge

transistor. If slew rate control is enabled, the sink condition is slew-rate controlled.

Afterwards the driver is switched into the resistive output mode (resistive path to source).

4.26

Short circuit detection / drain source monitoring

The Drain - Source voltage of each activated external MOSFET of the H-bridge is monitored

by comparators to detect shorts to ground or battery. If the voltage-drop over the external

MOSFET exceeds the configurable threshold voltage VSCd_HB (DIAG_x (CR 10) for longer

t > tSCd_HB the corresponding gate driver switches off the external MOSFET and the

corresponding drain source monitoring flag DS_MON_x (SR 2) is set. The DSMON_x bits

have to be cleared through the SPI to reactivate the gate drivers. This monitoring is only

active while the corresponding gate driver is activated. If a drain-source monitor event is

detected, the corresponding gate-driver remains activated for at maximum the filter time.

When the gate driver switches on, the drain-source comparator requires the specified

settling time until the drain-source monitoring is valid. During this time, this drain-source

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