ISL78692 operates with an input as low as 2.65V (cold crank case), reverse battery leakage of 700nA, 1% initial voltage accuracy, and ambient temperature range of -40˚C to +85˚C. This charger is designed to work with various types of AC adapters or a USB port. It operates as a linear charger when the AC adapter is a voltage source.
The typical applications of this device are automotive systems, eCall systems, and backup battery systems. The figure below shows the simple application circuit using Intersil ISL78692.
Theory of Operation
The ISL78692 is an integrated charger for single-cell Lithium
chemistry batteries. The ISL78692 functions as a traditional
linear charger when powered with a voltage source adapter.
When powered with a current-limited adapter, the charger
minimizes the thermal dissipation commonly seen in traditional
linear chargers.
As a linear charger, the ISL78692 charges a battery in the popular constant current (CC) and constant voltage (CV) profile. The constant charge current IREF is programmable up to 1A with an external resistor or a logic input. The charge voltage VCH has 1% accuracy over the entire recommended operating condition range. The charger preconditions the battery with a 10% typical of the programmed current at the beginning of a charge cycle until the battery voltage is verified to be above the minimum fast charge voltage, VTRICKLE. This low current preconditioning charge mode is named trickle mode. The verification takes 15 cycles of an internal oscillator whose period is programmable with a timing capacitor on the time pin. A thermal-foldback feature protects the device from the thermal concern typically seen in linear chargers. The charger reduces the charge current automatically as the IC internal temperature rises above +100°C to prevent further temperature rise. The thermal-foldback feature guarantees safe operation when the printed circuit board (PCB) is space limited for thermal dissipation.
As a linear charger, the ISL78692 charges a battery in the popular constant current (CC) and constant voltage (CV) profile. The constant charge current IREF is programmable up to 1A with an external resistor or a logic input. The charge voltage VCH has 1% accuracy over the entire recommended operating condition range. The charger preconditions the battery with a 10% typical of the programmed current at the beginning of a charge cycle until the battery voltage is verified to be above the minimum fast charge voltage, VTRICKLE. This low current preconditioning charge mode is named trickle mode. The verification takes 15 cycles of an internal oscillator whose period is programmable with a timing capacitor on the time pin. A thermal-foldback feature protects the device from the thermal concern typically seen in linear chargers. The charger reduces the charge current automatically as the IC internal temperature rises above +100°C to prevent further temperature rise. The thermal-foldback feature guarantees safe operation when the printed circuit board (PCB) is space limited for thermal dissipation.
To learn more about Intersil's ISL78692, click on the link below:
Highly Integrated Li-Ion Battery Charger
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