ISL6291
Li-ion/Li Polymer Linear Battery Charger

Key Features

• Integrated Linear Pass Element
• Integrated Charge Current Sensor
• No External Reverse Blocking Diode Required
• 1% Voltage Accuracy
• Programmable Current Limit Up to 2.0A
• Programmable End-of-Charge Current
• Trickle Charge an Over Discharged Battery
• Charge Current Thermal Foldback
• Simple Interface for Low-Cost Thermistor
• Accepts USB Bus Power
• Ambient Temperature Range: -20°C to 70°C
• Thermally-Enhanced 5x5 QFN Package (θ_JA = 33°C/W)

Description

The ISL6291 provides a low-cost integrated charger solution for single-cell Li-ion and Li Polymer rechargeable batteries. No external pass element, current sensing resistor, or reverse blocking diode is required with this solution.

The ISL6291 is a constant-current (CC)/constant-voltage (CV) charger. The constant charge current is programmable up to 2.0A with an external signal resistor. An internal trimmed current-sense circuit guarantees 10% accuracy, with no bulky external current-sense resistor. The constant voltage is either 4.1V or 4.2V. The charger always preconditions the battery with 1/10 of the programmed charge current at the beginning of a charge cycle, until it verifies that the battery can be fast-charged. A safety timer prevents over-charging a dead battery. The charging terminates as the charge current falls below the programmed minimum current during the CV mode. The charger automatically re-charges the battery when the battery voltage drops below a recharge threshold. A simple interface with an NTC thermistor avoids charging the battery outside a programmable temperature window. A thermalfoldback feature of the ISL6291 guarantees safe operation when the printed circuit board space is limited for thermal dissipation. The charger reduces the charge current automatically, as the internal temperature rises above a preset level, to prevent further temperature rise.

When the wall adapter is not present, the ISL6291 draws less than 1µA current from the battery. Two logic outputs provide the charging status and fault information, and an easy interface to system logic. A V2P8 pin outputs a 2.8V reference voltage that can be used to bias other circuits, or as an indication for the adapter presence.

The ISL6291 is packed in a thermally enhanced 5x5 QFN package. See the Technical Brief TB389 given in the Related Literature for more information related to the package.

Applications

• Handheld Devices
• Cell Phones
• PDAs
• Stand-Alone Chargers
• USB Bus-Powered Chargers