TAS2120 can be configured to function for different battery systems like single series cell (1S) Li-ion battery (2.5 V to 5.5 V) or 2-series cell (2S) series cell battery (4.7 V to 10 V). When the 2S battery is selected for the device, the diagram below shows the conceptual connections in the system to connect the 2S battery. When selected for 2S battery operation, the VBAT pin of the device is used for biasing internal blocks and needs to be supplied from external power source between 3.0 V to 5.5 V.

The internal battery voltage monitor needs to be switched to sense the voltage on the VBAT_SNS pin instead of the default sensing done on the VBAT pin. SEL_VBAT_MODE[1:0] configures the internal voltage monitor and the device configuration between 1S or 2S battery systems.

When SEL_VBAT_MODE[1:0] is set as '10', ie 2S mode of operation, the device internal bias voltage needs to be configured based on VBAT_BIAS_SELx registers. If the VBAT pin voltage is available from the center tap or half of the 2S battery voltage, the VBAT_BIAS_SEL1 needs to be set high. For other VBAT voltage configurations the VBAT_BIAS_SEL1 should be set low and appropriate VBAT_BIAS_SEL2 configuration should be selected.