Abstract
This paper presents a capacitive pressure sensor interface circuit design in 180 nm XH018 CMOS technology for an implantable capacitive pressure sensor, which has a wireless power supply and wireless data transfer function. It integrates full-bridge rectifiers, shorting control switches, low-dropout regulators, bandgap references, analog front end, single slope analog to digital converter (ADC), I2C, and an RC oscillator. The low-dropout regulators regulate the wireless power supply coming from the rectifier and provide a stable and accurate 1.8 V DC voltage to other blocks. The capacitance of the pressure sensor is sampled to a discrete voltage by the analog front end. The single slope ADC converts the discrete voltage into 11 bits of digital data, which is then converted into 1 kbps serial data out by the I2C block. The “1” of serial data is modulated to a 500 kHz digital signal that is used to control the shorting switch for wireless data transfer via inductive back scatter. This capacitive pressure sensor interface IC has a resolution of 0.98 mmHg (1.4 fF), average total power consumption of 7.8 mW, and ±3.2% accuracy at the worst case under a −20 to 80 °C temperature range, which improves to ±0.86% when operated between 20 and 60 °C.
Highlights
Pressure is an essential indicator of patient health and disease progression as it is highly regulated in different organs in the human body such as the bladder, heart, eye, and brain [1]
This capacitive pressure sensor interface IC has a resolution of 0.98 mmHg (1.4 fF), average total power consumption of 7.8 mW, and ±3.2% accuracy at the worst case under a −20 to 80 ◦ C temperature range, which improves to ±0.86% when operated between 20 and 60 ◦ C
The complete process of designing a low-power capacitive pressure sensor interface IC with wireless power and data transfer in a standard 0.18 μm CMOS technology has been described in the system and transistor levels
Summary
Pressure is an essential indicator of patient health and disease progression as it is highly regulated in different organs in the human body such as the bladder, heart, eye, and brain [1]. For a fully implantable device, sensor, sensor interface circuitry, wireless data telemetry, and wireless power are typically needed. AFE plus single-slope ADC with inductive power supply and data transfer are are investigated at the system level, described in detail at the circuit and transistor level, and investigated at at the the system system level, level, described described in in detail detail at at the the circuit circuit and and transistor transistor level, level, and and investigated presented with some experimental results. Achieves full functionality on a monolithic chip with presented with some experimental results. It with presented with some experimental results It achieves full functionality on a monolithic chip with features of capacitive pressure sensing, wireless power supply, and wireless data transfer. The following sections present the complete design of integrated capacitance interface. 3 with conclusions drawn in Section layout simulation results arepresented presented
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