L9660 datasheet(18/49 Pages) STMICROELECTRONICS

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Functional description

L9660

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DocID024714 Rev 2

Functional description

3.1

Overview

The L9660 is an integrated circuit to be used in air bag systems. Its main functions include

deployment of air bags. The L9660 supports 4 deployment loops.

3.2

General functions

3.2.1

Power on reset (POR)

The ASIC has a power on reset (POR) circuit, which monitors VDD voltage. When VDD

voltage falls below VRST1 for longer than or equal to tPOR, all outputs are disabled and all

internal registers are reset to their default condition. A second reset level, VRST2, also

monitors VDD but uses no filter time, so all outputs are disabled and all internal registers are

reset to their default condition when VDD falls below the reset threshold.

Figure 6. POR timing

3.2.2

RESETB

The RESETB pin is active low. The effects of RESETB are similar to those of a POR event,

except during a deployment. When a deployment is in-progress, the L9660 ignore the

RESETB signal.

However, it shuts itself down as soon as it detects a POR condition. When the deployment is

completed and RESETB signal is asserted, the L9660 disables its outputs and reset its

internal registers to their default states.

A de-glitch timer is provided for the RESETB pin. The timer protects this pin against

spurious glitches. The L9660 neglects RESETB signal if it is asserted for shorter than

tGLITCH. RESETB has an internal pull-up in case of an open circuit.

L9660 Datasheet(PDF) 18 Page - STMicroelectronics