ISL6291 Li-ion/Li Polymer Linear Battery Charger

The ISL6291 offers a cost-effective integrated charger solution for single-cell lithium-ion and lithium polymer rechargeable batteries. This solution does not require any external pass elements, current sensing resistors, or reverse blocking diodes. The ISL6291 functions as a constant-current (CC) and constant-voltage (CV) charger. The constant charge current can be programmed up to 2.0A using an external signal resistor. An internal trimmed current-sense circuit ensures 10% accuracy without the need for a bulky external current-sense resistor. The constant voltage can be set to either 4.1V or 4.2V. At the beginning of a charge cycle, the charger preconditions the battery with 1/10 of the programmed charge current until it confirms that the battery is capable of fast charging. A safety timer is included to prevent overcharging a dead battery. Charging terminates when the charge current falls below the programmed minimum current during the CV mode. The charger will automatically recharge the battery when the battery voltage drops below a designated recharge threshold. A straightforward interface with an NTC thermistor prevents charging the battery outside a programmable temperature range. The thermal foldback feature of the ISL6291 ensures safe operation in situations where printed circuit board space is limited for thermal dissipation. The charger automatically reduces the charge current as the internal temperature exceeds a predetermined level to prevent further temperature increases. When a wall adapter is not connected, the ISL6291 consumes less than 1 µA of current from the battery. Two logic outputs provide charging status and fault information, offering an easy interface to system logic. The V2P8 pin outputs a 2.8V reference voltage that can be used to bias other circuits or indicate the presence of an adapter. The ISL6291 is housed in a thermally enhanced 5x5 QFN package. For additional information regarding the package, refer to Technical Brief TB389 in the Related Literature.

The ISL6291 is designed for efficient charging of single-cell lithium-ion and lithium polymer batteries, making it suitable for a variety of portable electronic applications. Its integration of essential charging functions minimizes the need for external components, thereby reducing the overall footprint of the charging circuit. The programmable charge current allows designers to tailor the charging rate according to the specific requirements of the battery being used, enhancing flexibility in design.

The internal current sensing circuit not only simplifies the design by eliminating the need for an external resistor but also contributes to the overall accuracy of the charging process. The choice between 4.1V and 4.2V constant voltage settings allows for compatibility with different battery chemistries, ensuring optimal charging performance.

The preconditioning feature is particularly beneficial for maintaining battery health, as it prepares the battery for fast charging under safe conditions. The safety timer is a critical aspect of the design, protecting against potential overcharging scenarios that could damage the battery or reduce its lifespan.

The thermal foldback capability is essential in applications where space constraints may limit heat dissipation. By automatically adjusting the charge current in response to temperature increases, the ISL6291 ensures reliable operation while preventing overheating.

The low quiescent current draw of less than 1 µA when not connected to a wall adapter is advantageous for battery-powered devices, extending battery life during idle periods. The inclusion of logic outputs for charging status and fault conditions enhances the integration of the charger into larger systems, facilitating monitoring and control.

Overall, the ISL6291 represents a robust and efficient solution for battery management in portable electronics, combining advanced features with a compact design to meet the demands of modern applications.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 1 µA 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.

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