1FEATURES

• Eight-channel squib drivers for airbag

application

• Loop diagnostics monitor and reporting

• Two logic inputs providing independent safing

logic for enabling/disabling deployment

• Eight independent thermally protected High

Side drivers that can source deployment or

diagnostic current level to each squib load

• Eight independent avalanche voltage and

thermally protected Low Side drivers that can

sink deployment or diagnostic current level

from each squib load

• Each output capable of 1.2A/1.75A firing

current for typical 2ms/0.5ms

• SPI Slave Interface for serial bus

communication with parity check

• Firing VZx voltage range 10V to 35V, transients

up to 40V

• Programmable firing time up to 8.2 ms

• Common Load current settings for all

deployment loops, using registers

• Individual firing current timer limit set for each

deployment loop, using registers

• Firing current timer to monitor firing current

over deployment time for each deployment

loop

• Independent switch control for both high and

low side switches

• Diagnostic mode for fault checking

• Internal fault monitoring for safe operation

• A multiplex-able output buffer for analog

voltage measurements

• Use of external clamping devices on squib

pins is not required to protect the deployment

ASIC against substrate injection effects during

deployment due to dynamic shorts to ground

• An external pin connection to the

microprocessor ADC supply for ratio-metric

squib resistance measurement.

• 40V pin capability on all pins (except GNDx,

AGND, DGND, VCC5, VDDIO, AMX_OUT)

• Operating ambient temperature range: -40°C to

105°C

• Thermally enhanced 48-pin TSSOP DCA

PowerPad package

APPLICATIONS

• Squib Drivers for Airbag Application

DESCRIPTION

The TPIC71008 is an eight channel squib driver for airbags deployment in automotive applications. Each channel

consists of a high side and low side switch with independent control logic for protection against inadvertent

deployment. Both the high and the low side switches have internal current limit and over-temperature protection.

The IC registers are used for eight channel configuration, control and status monitoring. To prevent inadvertent

deployment, the high and the low side switches are turned on only if the proper configuration sequence is used,

two independent arming/safing inputs are active and multiple inputs to the deploy controller logic are at the

correct level. The registers are programmed using a serial communications interface.

To prevent excessive power dissipation the maximum active ON time for each channel is limited by

programmable Firing Time Out Timer. In addition, a current limit register is used to program the maximum current

through the switches during a deployment. The current limitation on the low side switch is larger than the

corresponding current limitation on the high side switch. During deployment, the low side switch is fully enhanced

and operates with RDS_ON mode, while the high side switch is in current regulation mode.

IC diagnostic functions monitor deployment pin voltages to facilitate High Side switch test, Low Side switch test,

squib resistance measurements, squib leakage measurement to battery or ground or leakage between any squib

channels. The squib leakage measurement does not require the squib load to be present and covers both Zx and

ZMx pins. Diagnostic information is communicated through the AMX_OUT pin (for analog signals) and SPI

mapped status registers (for status signals latched in digital core).

The high-side and low-side squib drivers have a diagnostic level current limit and a deployment level current limit.

The default current limit for high-side and low-side squib drivers is the diagnostic level current limit. The high-side

switch deployment current limit for all high-side drivers can be set to either 1.2 A min or 1.75 A min (see Table 1)

through SPI mapped registers and device EEPROM settings (see Table 2). The low-side switch deployment

current limit is not programmable and is fixed to a level greater than the high-side driver current limit. The ON

time duration for each individual squib driver can be programmed through SPI mapped registers.

The deployment sequence requires a specific set of software commands combined with external hardware

arming/safing logic inputs (TZ=H, IWD=L) to provide deployment capability. The turn-on sequence of the

high-side and low-side drivers is software controlled via SPI commands. The turn-off procedure is automatically

controlled by the deployment ASIC for the high side drivers, while the low side drivers turn-off procedure can be

controlled by the deployment ASIC or by software via SPI commands. After the programmed ON time

deployment has been achieved, the high-side driver is deactivated first. It is followed by the low-side driver

deactivation after approximately 100usec (in case of hardware control turn-off sequence device configuration), or

after SPI command for low side driver turn-off has been received from an external microcontroller (in case of

software control turn-off sequence device configuration).

The RESET_N is an active low input reset signal. This input will be released high by the power supply unit and/or

the external microcontroller once the external voltage supplies are within the specified limits. The external

microcontroller is required to configure and control device through the serial communication interface. Reliable

software is critical for the system operation.