L9788 datasheet(109/264 Pages) STMICROELECTRONICS

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DS12308 Rev 4

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L9788

High/low-side drivers - STARTER STR[1:3]

263

Figure 41. OFF state diagnostic HS config block schematic

In the HS mode we can have three different load conditions:



Normal Load, it means output driver connected to the load, No Fault Present, VOUT≤

V_OL Threshold;



Open Load, It means output driver disconnected to the load, Open Load Fault Present,

VHVT ≥ VOUT ≥ V_OL Threshold;



Short To VB, it means output driver shorted to VB voltage, Short To VB Fault Present,

VOUT > VHVT.

There is a bit IPUPD_EN_STRx in CONFIG_REG13 which is controlled by a MSC bit, it is

used by external µController if it is needed to switch on/off both pull up and pull down

diagnosis current.

There is a bit IPUPD_MODE in CONFIG_REG2 which is controlled by a MSC bit, it is used

by external uController if it is needed to switch on/off the bigger diagnosis

current(I_HS_PD1) in fast mode.

The Diagnostic in Off state is done by the following block:



An internal Buffer using the pull up/down currents is able to force the VOUTOPEN

voltage on the High-Side Driver Output when the driver is in Open Load Condition.



A comparator to detect the Open load Condition. The Open Load fault is detected when

the OUTx pin is VHVT >= VOUT>= V_OL Threshold for a time longer than Diag Filter

Time.



A comparator to detect the Short to VB Condition. The Short To VB fault is detected

when the OUTx pin is VOUT >= VHVT Threshold for a time longer than Diag Filter

Time.



Fast pull down current, this current is used to avoid the false short to VB diagnosis

when the driver switches off in Open load condition. This current switches on after the

falling edge of MSC command (driver in off state) and remains on until the Diag Filter

Time is expired or until the VOUT is < VHVT Threshold. (Note: if fast pull down current

is selected, the filter time Tflt_diagoff1 is suggested. Otherwise, the filter time

Tflt_diagoff2 is suggested).

HLS DRIVER in HS configuration

VBAT

OUTx

LOAD

PGND

L/R

I_LS_PU

VOUTOPEN

VTVB

VTOPEN

DIAGOL

DIAGHV

I_LS_PD

MSC Command

Driver

GADG0212161526PS

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