Linear’s USB PowerPath Manager Withstands 60V Inputs
Linear Technology Corp. introduced the LTC4090, an autonomous linear PowerPath™ manager, diode controller and stand-alone high input voltage battery charger for portable USB devices. For high efficiency charging, the switching front-end topology accommodates various inputs, including high voltage power sources up to 38V (60V max withstand capability) such as 12V regulated/unregulated ac-dc wall adapters, FireWire ports or automotive power. In addition, the IC accepts low-voltage power sources such as 5V wall adapters, USB ports and single-cell Li-Ion/Polymer batteries.
The LTC4090 features linear PowerPath control that provides power to the device while charging its single-cell Lithium battery from the USB bus or a wall adapter power supply. To comply with USB current limit specifications, the LTC4090 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 200mΩ low loss ideal diode, minimizing voltage drop and power dissipation. Onboard control circuitry is provided to drive an optional external PFET to reduce the overall ideal diode impedance below 50mΩ if required by the application, providing even higher efficiency operation.
The LTC4090’s front-end switching regulator features Bat-Track™ adaptive output control, greatly improving the efficiency of its 1.5A-capable battery charger as the internal switching regulator’s output voltage automatically tracks the battery voltage by 300mV. Instant-on operation ensures system power is available as soon as the input supply is available, even with a dead or missing battery.
The battery charger’s float voltage is preset at 4.2V with guaranteed 1.0% accuracy from -40 to 85°C. Charge current is said to be 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 5x/1x USB current limiting, thermal regulation, an NTC thermistor input for temperature-qualified charging, automatic recharging of the battery, reverse current blocking, and under-voltage lockout.
The LTC4090 is housed in a low-profile (0.75mm) tiny 22-pin 3mm x 6mm DFN package. 1,000-piece pricing starts at $3.25 each.
