L9788 datasheet(84/264 Pages) STMICROELECTRONICS

84 / 264 page

Low-side drivers

L9788

84/264

DS12308 Rev 4

7.1.3

ON/OFF state - Error in on status diagnosis

To avoid unwanted driving of power stages the consistency of gate driving signal with digital

command is always monitored inside the device. Each time a turn-on/turn-off signal is

output by the logic core its effectiveness is verified comparing it with the status of the output

voltage.

The main logic can check the consistence between inner logic and actual signal at output

pin reading the OpenLoad comparator or Short-To-Ground Comparator according to

Table 42.

The driver status diagnosis (STA) is activated by the MSC on command, the relative

comparator is filtered for Tsta filter time to validate the diagnosis. In case of MOS pre-driver

the selected blanking time Tblank is applied before filtering.

Note:

In case of activation of OVT[17] the STA diagnosis is not available.

In case of activation of relative driver OVC the STA diagnosis is available.

7.1.4

OFF state - short load and open load

The device provides off-state diagnosis for each driver channel. Simplified schematic of

implemented diagnosis is shown in Figure 30.

Table 41. Driver status diagnosis

Symbol

Parameter

Test condition

Min

Typ

Max

Unit

Tsta

Driver status

diagnosis filter time

Tested by scan

32.5

µs

Table 42. STA diagnosis for drivers

STA diagnosis for drivers

INJ,SOL,O2H, RLY,

STR in Low-side

configuration

STR in high-side

configuration.

MOS pre-driver

IGN

ON state

Detected by STG

comparator, if the

output pin voltage is

higher than VLVT, STA

fault is detected

Detected by Open load

comparator, if the

output pin voltage is

lower than V_OL, STA

fault is detected.

Detected by STG

comparator, if the

MOS_DRN pin voltage

is higher than VLVT,

STA fault is detected.

Same information

as STG bit.

OFF state

(for LS/HS/PDRV)

LS_ON state

(for IGN)

Detected by Open load

comparator or Short To

Ground comparator. If

the output pin voltage

is lower than V_OL or

lower than VLVT STA

fault is detected.

Detected by STG

comparator, if the

output pin voltage is

higher than VLVT, STA

fault is detected.

Detected by Open

load comparator, if the

MOS_DRN pin voltage

is lower than V_OL,

STA fault is detected.

Not able to detect.

STA processing

filtering

blanking+filtering

filtering

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