L9679P datasheet(42/272 Pages) STMICROELECTRONICS

部品番号	L9679P

部品情報	Automotive advanced airbag IC for mid/high end applications

PDF	272 Pages

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メーカー	STMICROELECTRONICS [STMicroelectronics]

ホームページ	http://www.st.com

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42 / 272 page

Start-up and power control

L9679P

42/272

DocID029275 Rev 1

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.

V

I1 ILEAK

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

I2 ILEAK

–

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

2IT



Vstart Vend 2Vstop



–

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

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

L9679P データシート(PDF) 42 Page - STMicroelectronics