High-sensitivity ultra-low-power electrode resistance monitoring circuit for cardiac pacemakers

An electrode resistance monitoring circuit utilizing current comparison is proposed and demonstrated for implantable cardiac pacemakers. The resistance detection circuit compares the electrode resistance with the reference resistance in a highly-symmetrical topology based on current reference. It works in deep sub-threshold region with ultra-low power consumption. However, it is able to achieve a resistance detection threshold as low as several kilo Ohm. The circuit is implemented in 0.35-μm CMOS process. It consumes only 164 nA in monitoring mode and achieves reliable resistance detection threshold of 4.5 kΩ. The measurement results of 50 samples verify that it’s qualified for application in implantable cardiac pacemakers.