A read-out IC for airbag

We present a mixed-mode read-out ASIC for airbag applications. It performs amplification and signal conditioning from a silicon acceleration sensor. The input signal is voltage proportional to the sensitivity of the acceleration with a maximum range of 56mVpeak for a VDD of 5V. The output is analog rail-to-rail without dc-offset. The chip contains anti-alias filtering, a SigmaDelta A/D converter, a serial clocked DSP for low and high pass filtering, a digital-to-analog converter, a smoothing filter, an output rail-to-rail buffer, a local oscillator and a serial interface for build-in selftest as well as permanent sensor test. It is fabricated using a 0.7-µm double poly - double metal CMOS process and has a size of 3.28 mm². The silicon prototype have been fully evaluated. An output THD of less than -60dB at 4.25Vp-p and an output noise less than 4mVp-p within the bandwidth of 0.2Hz ∼ 300Hz are realized. The power dissipation is 2.9mA@5V.