The UCC3911 is a two-cell lithium-ion battery pack protector IC that incorporates an on-chip series FET switch thus reducing manufacturing costs and increasing reliability. The IC's primary function is to protect both lithium-ion cells in a two-cell battery pack from being either overcharged or over-discharged. It employs a precision bandgap voltage reference that is used to detect when either cell is approaching an overcharged or over-discharged state. When on board logic detects either condition, the series FET switch opens to protect the cells.