L9680 datasheet(172/277 Pages) STMICROELECTRONICS

172 / 277 page

Deployment drivers

L9680

172/277

DocID029257 Rev 1

Figure 35. Deployment timer diagnostic sequence

Squib diagnostics with common SRx connected loops

In case of two SRx pins are intentionally connected together, the PD_CURR_CSR bit of the

Deployment Configuration register (DCR_x, where x = 0, 2, 4, 6, 8, A) must be used to

indicate which loop pairs have the common SRx connection. The purpose of this additional

bit is to control the pull-down current on each channel to be consistent with or without the

Common SRx connected loops. When the DCR_x(PD_CURR_CSR) bit is set for one loop

pair and the Deployment diagnostic is run on that loop pair, the pull-down current is disabled

on both channels of the loop pair selected.

For the squib channel pair with common SRx connection, to understand if the two SFx pins

are shorted together, the squib resistance measurement must be required with the following

setting: LPDIAGREQ[12:11]=11. In this way the ISRC current generator is enabled on the

channel selected by RES_MEAS_CHSEL[3:0] bits while the Differential Operational

Amplifier is connected on the other channel of the squib channel pair. If the short between

the two SFx pin is not present then the Squib resistance measurement results will be close

to 0, otherwise it will be half the real squib resistance.

Loop diagnostics control and results registers

Diagnostic tests and channels for each test are controlled through the Loop Diagnostic

Request Register (LPDIAGREQ), diagnostic results are stored in the Loop Diagnostic

Status Register (LPDIAGSTAT).

L9680 Datasheet(PDF) 172 Page - STMicroelectronics