For high-efficiency charging, their switching topology accommodates various inputs, including high-voltage power sources up to 36V (40V max) such as 12V AC-DC wall adapters, FireWire ports or automotive batteries. In addition, they accept low-voltage power sources such as 5V wall adapters or USB inputs and single-cell Li-Ion/Li-Polymer batteries. The LTC4089/-5 features PowerPath control that provides power to the USB peripheral device and charges the peripheral's single-cell Lithium battery from the USB bus or a wall adapter power supply and also allows for instant-on operation even with a depleted or missing battery.
To comply with USB current limit specifications, the LTC4089/-5 automatically reduces battery charge current as the system load current increases. To ensure that a fully charged battery remains topped off when the bus is connected, the IC directs power to the load through the USB bus rather than extracting power from the battery. Once all power sources are removed, current flows from the battery to the load through an internal 200mohm low loss ideal diode, minimizing voltage drop and power dissipation.
Onboard circuitry is provided to drive an optional external PFET to reduce the overall ideal diode impedance below 50mohm if required by the application, providing higher efficiency operation. The LTC4089's switching regulator features Bat-Track adaptive output control which greatly improves the efficiency of its 1.2A-capable battery charger as the switching regulator's output voltage automatically tracks the battery voltage.
The LTC4089-5 provides a fixed 5V output from the high-voltage input to charge single-cell Li-Ion/Li-Polymer batteries. The battery charger's float voltage is preset at 4.2V with 'guaranteed' 1% accuracy from 0C to 85C.
Charge current is easily programmed using a single resistor. For battery pre-conditioning and qualification, fully discharged cells are automatically trickle charged at 10% of the programmed current until the cell voltage exceeds 2.9V.
Total charge time for charge termination is programmed by an external capacitor, and a C/10 charge current detection output is provided. Additional functions include thermal regulation, an NTC thermistor input for temperature-qualified charging, automatic recharging of the battery, reverse current blocking, and under-voltage lockout. The LTC4089/-5 is housed in a low-profile (0.
75mm) tiny 22-pin 6mm x 3mm DFN package, and is 'guaranteed' for operation from -40C to 85C, says the company.
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