Research on digital silicon gyroscope interface circuit based on bandpass sigma-delta modulator

This paper presents a novel digital silicon gyroscope interface circuit, designed by 0.35 μm BCD process, and the chip area is 4.8 mm ∗ 5.0 mm. The traditional noise model of charge amplifier decomposes the noise into voltage noise and current noise. But the test results show that current noise accounts for a large proportion, which is not consistent with the theoretical model. Through the analysis of experimental data and the study of operational amplifier’s working principle in charge amplifier, a new noise model is established, which makes the experimental data closer to the theoretical model. The design makes use of the bandpass characteristics of the bandpass sigma–delta modulator consistent with the sensitive structure of the silicon gyroscope, and optimizes the digital principle of the silicon gyroscope. The digital demodulation of bandpass sigma–delta modulator (BP SDM) can directly separate the in-phase component from the orthogonal component, which eliminates the tedious design of carrier signal digitization and multi-digital filtering, simplifies the frame structure of the whole digital silicon gyroscope system and reduces the design difficulty and physical cost. The ASIC of silicon gyroscope digital interface circuit is tested in combination with the sensitive structure. The noise density of 0.0014∘/s/Hz^1/2, zero stability of 1∘/h (1σ) and 0.2∘/h (Allen variation). The test of ASIC and the whole machine proves the correctness of the theoretical model, which reflects the correctness of the performance of the digital interface circuit of silicon gyroscope.