C8051F91x-C8051F90x Single/Dual Battery, 0.9–3.6.
Silicon Laboratories
C8051F911 - 12/10-Bit ADC MCU
C8051F91x-C8051F90x Single/Dual Battery, 0.9–3.6 V, 16–8 kB, SmaRTClock, 12/10-Bit ADC MCU Ultra-Low Power - 160 uA/MHz in active mode (24.5 MHz clock.