90dB Dynamic Range, Multi-Channel Data Acquisition ASIC for SONAR Application

The data acquisition & processing system is an important part of the sonar signal measurement system. This paper presents a stable, low noise, high performance (in-terms of noise & gain), multi-channel underwater acoustic signal conditioning system realized on an ASIC. The signal conditioning circuit having OTA with Class-AB output stage to drive the low impedance load, chopper-based stabilization, temperature independent OTA biasing scheme for SDM ADC, on-chip calibration & BIST setup are some of the innovative features incorporated in this IC. The ASIC is designed in 180nm CMOS process having all essential features of SONAR platforms using Cadence suit. Simultaneous acquisition of multi-channel analog signals (10uV-50mV) and accurate digital conversion circuits are realized and integrated on the chip. The data acquisition ASIC (8-channels) consists of low noise chopper-based frontend amplifier (noise ∼ 75nV i.e.-142dB) followed by signal conditioning chain and a 24-bit sigma delta ADC (SNDR ∼ 90dB). The ASIC occupies 8.5 × 8.5 sq.mm area and consumes 125mW/channel of power.