L9679P datasheet(42/279 Pages) STMICROELECTRONICS

No de pièce	L9679P

Description	Automotive advanced airbag for mid/high end applications and cut-off battery IC

PDF	279 Pages

Scroll/Zoom	100%

Fabricant	STMICROELECTRONICS [STMicroelectronics]

Site Internet	http://www.st.com

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42 / 279 page

Start-up and power control

L9679P

42/279

DS11627 Rev 7

The user can decide the charge and discharge time based on the ER CAP used in

application, in order to maximize the differential voltage and then improve the accuracy.

Anyway, a timeout on ER Discharge current has been implemented to prevent thermal

issue, so the discharge time cannot be longer than 350 ms.

Figure 16. ER CAP measurement timing diagram

The following formulas can be used to retrieve the ER CAP value from the voltage and

timing measurements.

T1 = discharge time

T2 = charge time, same as discharge time

T1 = T2 = T



V1 = Vstart - Vstop



V2 = Vend - Vstop

I1 = discharge current

I2 = charge current, same as discharge current

I1 = I2 = I

ILEAK = leakage current

ESR > 0

VER (t)

ER_DISCHARGE

ER_CHARGE

ESR = 0

Vstart

Vstop

Vend

GAPGPS02262



V1 V2

I1 ILEAK

---------------------------T1

I2 ILEAK

–

--------------------------T2

2 I T

 

Vstart Vend 2 Vstop



–

----------------------------------------------------------------

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