A 1.9 nW Timer and Clock Generation Unit for Low Data-Rate Implantable Medical Devices

Abstract

This work presents a thyristor-based low power timer for wake up control of implantable monitoring devices, as well as a clock generation unit based on said approach. By using CMOS thyristors as delay elements in a ring oscillator, major drawbacks of conventional ring oscillators, such as a high stage count of inverters and capacitors with large currents flowing t o g round d uring s witching, c an b e o vercome. T his is particularly relevant for low frequency generation where these issues become even more critical in terms of power and area. Thyristors generate larger delays per stage while presenting a faster transition when switching between states, when compared to a typical CMOS inverter, an thus demand a smaller dynamic power. Timer, clock gating control and clock generation units were combined, implemented, and fabricated in 350 nm CMOS technology. The timer is able to wake up the clocking system (and hence a digital control unit) every 32.45 s with a power budget of less than 2 nW, while the clock generation unit produces a signal of 8.2 kHz.