摘要
This paper presents a chip designed for wireless intra-cardiac monitoring systems. The design consists of a three-channel analog front-end, a pulse-width modulator featuring output-frequency offset and temperature calibration, and inductive data telemetry. By employing a resistance boosting technique in the instrumentation amplifier feedback, the pseudo-resistor exhibits lower non-linearity, leading to a total harmonic distortion of below 0.1&null Furthermore, the boosting technique enhances the feedback resistance, leading to a reduction in the size of the feedback capacitor and, consequently, the overall size. To make the modulator&null output frequency resilient to temperature and process changes, coarse and fine-tuning algorithms are used. The front-end channel is capable of extracting the intra-cardiac signal with an effective number of bits of 8.9, while exhibiting an input-referred noise of less than 2.7&null notation="LaTeX">$mu V_{rms}$</tex-math></inline-formula>, and consuming 200 nW per channel. The front-end output is encoded by an ASK-PWM modulator, which drives an on-chip transmitter at 13.56&null The proposed System-on-Chip (SoC) is fabricated in a 0.18&null notation="LaTeX">$mu m$</tex-math></inline-formula> standard CMOS technology and consumes 4.5&null notation="LaTeX">$mu W$</tex-math></inline-formula> while occupying 1.125 <inline-formula><tex-math notation="LaTeX">$mm^{2}$</tex-math></inline-formula>.