L9679P datasheet(157/272 Pages) STMICROELECTRONICS

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L9679P

Deployment drivers

271

The high level block diagram for the deployment drivers is shown below:

Figure 30. Deployment driver block

8.1.1

Deployment current selection

Deployment current is programmed for all channels using the Deploy Configuration Register

(DCRx) shown in Section 7.3.7.

The deploy time selection allows the device to deploy for a time up to 4.032 ms. Careful

considerations should be done in order to avoid damage on the squib driver section for

excessive thermal heat. In order to prevent device damage, it is suggested to avoid

excessive voltage drop between SSxy and SFxy. In case the 1.75 A deployment current

level is selected, the voltage drop across the pins should be limited to maximum 17 V for

deployment times longer than 0.7 ms and up to 2 ms and 15 V up to 3.2 ms. In case 1.2 A is

selected, the voltage drop should be limited to maximum 22 V for deployment times longer

than 2 ms and up to 3.2 ms.

8.1.2

Deploy command expiration timer

Deploy commands are received for all channels using SPI communications. Once a deploy

command is received, it will remain valid for a specified time period selected in the

Deployment configuration registers (DCR_x). The deploy status and deploy expiration timer

can be read through the Deployment status registers (DSR_x). The deploy expiration timer

is selectable via 2 bits and the maximum programmable time is 500ms nominal.

L9679P Datenblatt(PDF) 157 Page - STMicroelectronics