A 150pW program-and-hold timer for ultra-low-power sensor platforms

Lifetime and form factor are two critical concerns for emerging sensor platforms, particularly for applications such as implantable medical devices. The limited energy from power sources, typically either microfabricated batteries or scavenged energy, remains one of the biggest challenges for such platforms. Reducing power consumption can lower system volume and extend lifetime. To achieve very low power consumption aggressive voltage scaling has been applied in recent microsystems [1, 2]. The average power consumption of sensor platforms, which are often low duty cycle, can be greatly reduced by applying strong power gating while idling [3]. A key component in power gating is the timekeeping device while the system is in the idle mode. Since the timer is always active, it is often the dominant source for energy loss and must oscillate at a low frequency (e.g., from sub-Hz to 10Hz).