A PMOS-based Programmable Stimulator with Adaptive Charge Pump for Cardiac Pacemakers

Conventional pacemaker stimulators adopt an NMOS-based voltage multiplier requiring higher gate drive voltage than the impulse voltage which is normally provided by an auxiliary charge pump. Such a scheme is neither good for power efficiency nor friendly to robust long-term operation due to higher voltage stress. This paper proposes a PMOS-based stimulator with adaptive regulation to enhance not only the power efficiency but also the reliability. Thanks to the PMOS-based scheme, the required driving voltage from the auxiliary voltage multiplier is much less than the NMOS-based counterpart. Designed with 3 operation modes, both the auxiliary voltage multiplier and main charge pump can adaptively adjust their voltage multiplication factor (1×, 2×, or 3× of the 2.8-V battery voltage) to improve the efficiency while offering an impulse range of 0.1 ~ 8.4 V with 0.1-V resolution. Designed in a 0.18-μm BCD process, the stimulator preserves a maximum power efficiency of 67.77% and a relative error range of 3.8~10%. The active area of the 2 stimulator channels is 1.62×1.03 mm
²
.