C8051F93x-C8051F92x Single/Dual Battery, 0.9–3.6.
Silicon Laboratories
C8051F921 - 10-Bit ADC MCU
C8051F93x-C8051F92x Single/Dual Battery, 0.9–3.6 V, 64/32 kB, SmaRTClock, 10-Bit ADC MCU Supply Voltage 0.9 to 3.6 V - One-Cell Mode supports 0.9 to 1.