L9654 datasheet(30/59 Pages) STMICROELECTRONICS

30 / 59 page

Functional description

L9654

30/59

DocID14218 Rev 3

4.10.8

High-side MOS diagnostic

When L9654 receives an SPI command to initiate the high-side MOS diagnostic, the

following conditions are verified before turning on the high-side MOS:



VSQL greater than SGTH threshold voltage



VSQH less than SBTH threshold voltage

If both conditions above are satisfied, the high-side MOS diagnostic is executed. Otherwise,

it is ignored and both bit D13 and bit D7 in SPI diagnostic are set.

Upon detection of the following conditions, the high-side driver is turned off and the

diagnostic, within the specified time, tPROP_DLY, is terminated



VSQH greater than SBTH threshold voltage



(VSQHx – VSQLx) greater than VI_TH



VSQL less than SGTH threshold voltage

The state of each comparator above is reported through SPI. When L9654 detects one of

the above conditions, it sets the respective SPI status bit to indicate the condition. Any of the

above conditions is considered as normal in a high-side MOS diagnostic.

The high-side driver is turned off when tTIMEOUT is expired. A fault detection filter, tFLT_DLY, is

provided to protect against short-transients on SQH and SQL pins.

4.10.9

Loss of ground

When any of the power grounds (GND0 – 7) are lost, no deployment can occur to the

respective deployment channels. 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. Also, the resistance

measurement result is on the low end of the resistance range.

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