L9679P datasheet(157/279 Pages) STMICROELECTRONICS

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DS11627 Rev 7

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L9679P

Deployment drivers

278

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 each channel using the Deploy Configuration

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/pyroswitch 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 500 ms nominal.

SSxy

SFx

SRx

SGxy

22nF

Rsquib

LS_ON

HS_ON

To deploy

current >90%

counter

5%R

95%R

R/2000

(50m )

OP with switching

Offset compensation

IREF= 1mA

2000 x IREF

Open to short comp

Vclamp >35V

Same power

transistor

VINT3V3

Enable _HSx

EN_ISINK

OPphase

LS_OC_Comp

GNDSUB1&2

Loss ground

diode

LS_Loss _Gnd

Ipulldown

Ilimit = 70mA typ

Enable _LSx

Passive

Switch -off

Active

Switch -off

Passive

Switch -off

Active

Switch -off

SSxy

VINT3V3

GAPGPS02279

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