Linear Technology battery chargers

Linear Technology has introduced the LT3650-4.1 and LT3650-4.2 compact, monolithic, high-voltage battery chargers for single-cell Li-Ion polymer batteries.

The device’s switchmode architecture minimises power dissipation without compromising board space. The LT3650-4.1/4.2 operates from 4.75 to 32 V and has a 40 V absolute maximum rating for added system margin.

User-selectable timer or C/10 termination requires no external microcontroller and simplifies the design. Charge current is programmable and dynamically adjustable up to 2 A; the power device is integrated on chip to save board space. The device does not require external high-precision resistors to set the float voltage, further saving cost and space.

The LT3650-4.1 offers a 4.1 V battery float voltage, allowing high temperature safety margin, while the LT3650-4.2 features a 4.2 V final charge voltage for optimised battery run time.

The LT3650-4.1/4.2’s high operating frequency of 1 MHz and current mode architecture allow the use of small inductors and capacitors, minimising noise and filtering needs. Final float voltage accuracy is specified at ±0.5%, charge current accuracy is ±5% and C/10 detection accuracy is ±2.5%.

Once charging is ended, the LT3650-4.1/4.2 automatically enters a low current standby mode that reduces the input supply current to 85 µA. In shutdown, the input bias current is reduced to 15 µA. It maximises battery life during all non-charging periods, draining less than 1 µA from the battery.

For safety and autonomous charge control, it includes automatic restart and preconditioning, a thermistor input for temperature-qualified charging, programmable input current limit, bad battery detection and binary coded status output pins.