ASIC Design For Digital Calipers With Capacitive Transducers

As basic measuring tools, mechanical calipers have been widely used in manufacture industry. But its difficult reading, low accuracy and single function can not meet the need of modern manufacture. With the development of electronic technology it makes easier to integrate all functions of production into one chip, which can reduce cost and volume of system, increase capability, and decrease power dissipation. The digital calipers with advantages of small volume, small output impedance, high sensibility, wide temperature range, low power dissipation, little parasitic capacitance will be used more widely.Firstly, displacement-measuring principle of digital calipers is analyzed and capacitive transducers model applied to data processing is presented with Verilog-A and simulated by Spectre. Secondly, logic circuits are designed to meet the demand of capacitive system, and three important parts of them are researched as follows: charge pump circuit is designed to reduce power dissipation. Demodulation circuit is designed to demodulate and magnify the output signals of capacitive transducers. Phase discriminator is designed to distinguish the different phase between input signal and output signal of capacitive transducers. Meanwhile, logic circuits above are simulated and validated by Hspice. Thirdly, layout based on 3μm CMOS Process is designed and checked. Finally, this novel chip with high integrity, low power dissipation and mixed signal tapes out and is sold in the market.