L9788 datasheet(124/264 Pages) STMICROELECTRONICS

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Pre-drivers - ExtFET (MOS_Gate1/2/3/4/5) - PRD[1:5]

L9788

124/264

DS12308 Rev 4

9.2

ON state diagnostic

In the On state of pre-driver, the diagnosis will compare the Drain-source voltage with the

threshold generated internal. If MOS_DRAIN_X>Vth_DS_XXX (PRDx_VDS[0:2]

CONFIG_REG5/ CONFIG_REG6 / CONFIG_REG7)for a filter time, the Drain short to

battery fault will be confirmed. The internal comparator reads the voltage on drain pin versus

a dedicated GND sense pin (PIN X) that at application should be connected on the source of

external mos. Starting from the condition ON state a programmable blanking time (MSC

CONFIG_REG16=PRDx_BLK[1:0]) is applied to prevent the detection of the short-to-

battery fault. The blanking time is not applied when the driver is already ON.The pre-driver

will switch OFF and the fault will be latched until the Read_Diag_CMD action. This bit can

be reset by every Read Diag Communication. To re-activate ON the power stage in this two

following conditions:



The MSC command still High, when the Fault OVC Bit is read by MSC communication.



The MSC command becomes Low and then again High.

When Bit MSC_O2HPredr_1 = 1 the VDS comparator of predriver 1 is ignored.

When Bit MSC_O2HPredr_3 = 1 the VDS comparator of predriver 3 is ignored.

When Bit MSC_O2HPredr = 1 the VDS comparator of predriver 2 (or 4) is enabled

immediately with the turn ON command of Predriver (and checked by logic after the

blanking time), while when Bit MSC_O2HPredr = 0 the VDS comparator of corresponding

channel is enabled after selected blanking time.

The over current protection can be done reading the voltage on external Rshunt using the

VDS comparator of predriver 2&4.

9.3

ON/OFF state - Error in status diagnosis

Refer to Section 7.1.3.

9.4

Error handling

Table 53. Pre-driver - ExtFET error handling

Type of error

Detection

condition

Action

Clear

MSC flag

Restart condition

Driver diagnostic

Overcurrent (OVC)

Driver on

Driver is put in off state.

The fault is latched in

MSC diagnosis register.

On read

At MSC read of diagnosis

is still high. If MSC

command is low and high

again.

Short to ground (STG)

Driver off

The fault is latched in

MSC diagnosis register.

On read

L9788 Datasheet(PDF) 124 Page - STMicroelectronics

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