Ultra-low Power Readout Circuit Design and Simulation using Dynamic Wheatstone Bridge Technique for Implantable Body Temperature Sensor Application

• Published in: Journal of semiconductor technology and science Vol. 25; no. 4; pp. 335 - 345
• Main Authors: Lim, Jounghoon, Kim, Jong-Pal
• Format: Journal Article
• Language: English
• Published: 대한전자공학회 31.08.2025
• Subjects: 전기공학
• DOI: 10.5573/JSTS.2025.25.4.335
• ISSN: 1598-1657

An ultra-low power consumption body temperature circuit for electroceuticals is proposed. Electroceuticals implanted in the body for nerve signal measurement and nerve stimulation can cause short-term or long-term infections, so it is necessary to monitor temperature increases due to inflammation. A Wheatstone bridge is used to read the resistance value of the thermistor mounted on the neural electrode interface. To reduce the current consumption, a dynamic Wheatstone bridge technique is proposed. The current is supplied only for a short time to obtain the temperature information, and the temperature information is obtained once from the bridge in the order of the external thermistor and the built-in resistor, and the temperature information is obtained again by flipping the bridge in the order of the built-in resistor and the external thermistor. Temperature information sampled over a short period of time is stored in the S&H block for use by the VCO in the rear end. The following VCO and TDC both operate at 0.6 V for low power consumption. The post-layout simulation results showed a sensitivity of 2230 digits/degree and a nonlinear error of −0.05/+0.08◦C in the 34 to 42◦C range, satisfying the ASTM thermometer standards. Power consumption was 112 nW, which is small enough to be incorporated into implantable devices. KCI Citation Count: 0