UCC3911-1

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.

A negative feedback loop controls the FET switch when the battery pack is in either the overcharged or over-discharged state. In the overcharged state the action of the feedback loop is to allow only discharge current to pass through the FET switch. In the over-discharged state, only charging current is allowed to flow. The op amp that drives the loop is powered only when in one of these two states. In the over-discharged state the chip enters sleep mode until it senses that the pack is being charged.

The FET switch UCC3911 is driven by a charge pump when the battery pack is in a normally charged state to achieve the lowest possible RDSON. In this state the negative feedback loop's op amp is powered down to conserve batterypower. Short circuit protection for the battery pack is provided and has a nominal delay of 100s before tripping. An external capacitor may be connected between CDLY and B0 to increase this delay time to allow longer overcurrent transients.

A chip enable (CE) pin is provided that while held low, inhibits normal operation of the chip to facilitate assembly of the battery pack.

The UCC3911 is specified for operation over the temperature range of −20°C to +70°C, the typical operating and storage temperature range of lithium-ion batteries.