This study proposes a front-end readout circuit as an encoder chip for magneto-resistance (MR) linear scales. A typical MR sensor consists of two major parts: one is its base structure, also called the magnetic scale, which is embedded with multiple grid MR electrodes, while another is an “MR reader” stage with magnets inside and moving on the rails of the base. As the stage is in motion, the magnetic interaction between the moving stage and the base causes the variation of the magneto-resistances of the grid electrodes. In this study, a front-end readout IC chip is successfully designed and realized to acquire temporally-varying resistances in electrical signals as the stage is in motions. The acquired signals are in fact sinusoids and co-sinusoids, which are further deciphered by the front-end readout circuit via newly-designed programmable gain amplifiers (PGAs) and analog-to-digital converters (ADCs). The PGA is particularly designed to amplify the signals up to full dynamic ranges and up to 1 MHz. A 12-bit successive approximation register (SAR) ADC for analog-to-digital conversion is designed with linearity performance of ±1 in the least significant bit (LSB) over the input range of 0.5–2.5 V from peak to peak. The chip was fabricated by the Taiwan Semiconductor Manufacturing Company (TSMC) 0.35-micron complementary metal oxide semiconductor (CMOS) technology for verification with a chip size of 6.61 mm 2 , while the power consumption is 56 mW from a 5-V power supply. The measured integral non-linearity (INL) is ?0.79–0.95 LSB while the differential non-linearity (DNL) is ?0.68–0.72 LSB. The effective number of bits (ENOB) of the designed ADC is validated as 10.86 for converting the input analog signal to digital counterparts. Experimental validation was conducted. A digital decoder is orchestrated to decipher the harmonic outputs from the ADC via interpolation to the position of the moving stage. It was found that the displacement measurement error is within ±15 μm for a measuring range of 10 mm.
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机译：这项研究提出了一种前端读取电路，作为磁阻（MR）线性标尺的编码器芯片。典型的MR传感器由两个主要部分组成：一个是其基本结构，也称为磁性标尺，它嵌入了多个栅格MR电极，而另一个是“ MR读取器”载物台，内部装有磁体并在磁体的轨道上移动。基础。当平台移动时，移动平台和基座之间的磁性相互作用导致栅极的磁阻发生变化。在这项研究中，成功设计并实现了前端读取IC芯片，以在平台移动时获取电信号中随时间变化的电阻。所采集的信号实际上是正弦波和余弦波，它们由前端读出电路通过新设计的可编程增益放大器（PGA）和模数转换器（ADC）进一步解密。 PGA经过专门设计，可将信号放大到最大动态范围和最高1 MHz。设计了一个用于模数转换的12位逐次逼近寄存器（SAR）ADC，在从峰到峰的0.5-2.5 V输入范围内，最低有效位（LSB）的线性性能为±1。该芯片由台湾半导体制造公司（TSMC）制造的0.35微米互补金属氧化物半导体（CMOS）技术进行验证，芯片尺寸为6.61 mm 2，而5V电源的功耗为56mW。测得的积分非线性（INL）为〜0.79–0.95 LSB，而差分非线性（DNL）为〜0.68–0.72 LSB。设计的ADC的有效位数（ENOB）已验证为10.86，可将输入模拟信号转换为数字对应信号。进行了实验验证。精心设计了一个数字解码器，以通过内插法将ADC的谐波输出解码到移动台的位置。发现对于10mm的测量范围，位移测量误差在±15μm内。
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