L9654 datasheet(27/59 Pages) STMICROELECTRONICS

Part #	L9654

Description	Quad squib driver and dual sensor interface ASIC for safety application

PDF	59 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

Logo

27 / 59 page

DocID14218 Rev 3

27/59

L9654

Functional description

Figure 14. Continuity diagnostic flow chart

4.10.3

Short to battery

A short to battery condition is detected when the voltage on SQH is greater than SBTH

threshold voltage.

4.10.4

Short to ground and open circuit

A short to ground or an open circuit condition is detected when the voltage on SQL is less

than SGTH threshold voltage. A resistance measurement is utilized to differentiate between

a short to ground or an open circuit condition.

4.10.5

Resistance measurement

During a resistance measurement, both ISRC and ISINK are switched on. An analog voltage

on AOUT pin is provided. AOUT pin is a 5V analog pin, which is connected to the ADC input

of a processor. This pin provides the resistance-measurement voltage, which corresponds

to the voltage difference across SQH and SQL according to the following formula:

Vaout = VDD/10 + Rsquib · Isrc · 10.

The accuracy in the range of Rsquib is classified as followings:

0 < Rsquib ≤ 3.5 Ω

±95 mV

3.5 < Rsquib ≤ 10 Ω ±5 %

L9654 Datasheet(PDF) 27 Page - STMicroelectronics