This chart shows the voltage supply range of single battery cells and combinations of battery cells. In the earlier C8051F9xx families, there was a gap in the input operating range of the supplies for the device. This was due to the fact that the supply range was configured through the pin settings of the device. In one cell mode, the upper limit to the supply was 1.8V and the lower limit was 0.9V. In the two cell mode, the lower limit was 1.8V. With some of the new devices in the C8051F9xx family, the input voltage can span the entire input supply range from 0.9V to 3.6V.