L9788 datasheet(122/264 Pages) STMICROELECTRONICS

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

L9788

122/264

DS12308 Rev 4

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

Figure 48. LS External MOSFET Pre-Driver Stage

9.1

LS external MOSFET pre-driver

These 5 pre-drivers are designed to drive LS external MOSFET Load. They are driven by

MSC command.

The push-pull stage is made up of limited source current and sink current. The voltage of

MOS_Drain is monitored for diagnosis.

The driver has the following detection diagnosis:



_Drain short to battery @ pre-driver = On state



_Drain short to ground @ pre-driver = Off state



_Drain open load @ pre-driver = Off state

Predriver1 & Predriver3 can be used to drive ExtMos for O2H Load.

For these two predrivers there is the possibility to select a lower gate current and sink

current (typ = 250 µA).

A dedicated MSC bit is used to select the predriver O2H function (Bit O2H_PDRV =

CONFIG_REG_16_1[7:6]). Considering that this sink/source current is very low the logic will

switch to the selected higher sink/source current after the cmd delay time (typ 150 µs for

CONFIG_REG20[7]=PDRV_O2H_DLY=0 or 300 µs

CONFIG_REG20[7]=PDRV_O2H_DLY=1). After the CMD delay time the current used is the

one selected by CONFIG_REG4=PRDx_IDRV[1:0].

When the Predriver is used for O2H load the overcurrent detection can't be done using a

VDS comparator due to slow voltage slew-rate, for this reason an external Rshunt has to be

used.

GADG0512161207PS

GND1

MOS_Source

MOS_Gate

MOS_Drain

VBAT

Load

MSC Command

LS ExtNMOS Pre-Driver

OFF state

Drain short to Gnd, OL

ON state

Drain short to battery

Driver

VB_IN

I_SOURCE

I_SINK

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