L9660 datasheet(29/49 Pages) STMICROELECTRONICS

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L9660

Functional description

High side safing diagnostics

When the command is received the L9660 activates IHSS on the selected VRESx. The

diagnostics measures the difference between VSDIAG and VRESx. The internal

comparator detects open, short or normal condition based on the differential voltage

between VSDIAG and VRESx.

The results are reported in the next SPI message using bits HSS1 and HSS0 as indicated in

the following table. Once the command is issued the voltages are captured on the next

falling edge of CS_D.

Voltage measurement diagnostics (VRESx)

When the command is received the L9660 activates a comparator for the selected channel.

A 2 bit indication of the state of the VRESx pins is reported as indicated below. The results

are reported in the next SPI message. Once the command is issued the voltages are

captured on the next falling edge of CS_D.

Loss of power ground

When any of the power grounds (GND0 – 3) are lost, no deployment can occur on the

respective deployment channels because the low side driver is inactive. The high side driver

for the respective channel can still be activated.

A loss of ground condition on one or several channels does not affect the operation of the

remaining channels. When a loss of ground condition occurs, the source of the low side

MOS is floating. In this case, no current flows through the low side driver.

This condition is detected as a fault by a low side MOS diagnostic. No additional faults are

reported from any other diagnostic due to this condition.

Table 12. Diagnostic Mode HSS selection

Condition

HSS1

HSS0

(VSDIAG-VRESx) < VHSSSHORT_th

VHSSSHORT_th < (VSDIAG-VRESx) < VHSSOPEN_th

VHSSOPEN_th < (VSDIAG-VRESx)

Table 13. Diagnostic mode 3 VRESx selection

Condition

VR1

VR0

VRESx < VVRESXLO_th

VVRESXLO_th < VRESx < VVRESXHI_th

VVRESXHI_th < VRESx

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