A CMOS sensor and signal conversion chip for monitoring arterial blood pressure and temperature

In medical intensive care, measurement of vital blood parameters is time-consuming and can be inconvenient to the patient. A system which processes the signals of the on-chip pressure and temperature sensors is presented. This includes signal conditioning and amplification using switch-capacitor techniques. Multiplexing some blocks helps to reduce chip area. To minimize noise sensitivity, digital transmission using a pulsewidth modulated signal is implemented. This also reduces the number of connections to five wires for power and ground, a clock for timing and running the switch-capacitor circuitry, and two lines for digital transmission and control. Using a 3- mu m CMOS process optimized for highly reliable analog circuits, the chip size can be limited to 7.2*0.7 mm/sup 2/. The chip can be embedded in a catheter 1 mm in diameter, at the same time allowing injection of medicine directly into the arterial blood stream. The catheter chip presented is part of a monitoring system that allows the doctor to do online analysis of blood pressure and temperature.<>