Synchronous monolithic 1-Cell Li-Ion/Polymer battery charger

Charge current is programmable and dynamically adjustable up to 4A; fully integrated synchronous power devices minimise power dissipation and save board space. User-selectable timer or C/10 termination requires no external microcontroller and simplifies the design. The LT3651-4.2 does not require external high-precision resistors to set the float voltage, further saving cost and space. Applications include industrial handheld instruments, 12 to 24V automotive and heavy equipment applications, desktop cradle chargers and notebook or tablet computers. The programmable switching frequency (200kHz to 1MHz) of the LT3651-4.2 enables the designer to balance solution size, power loss, and filtering needs. Synchronous operation enables charging efficiencies as high as 90%. Final float voltage accuracy is +/-0.5%, charge current accuracy is +/-7.5% and C/10 detection accuracy is +/-4%. Once charging is terminated, the LT3651-4.2 automatically enters a low current standby mode which reduces the input supply current to 80uA. In shutdown, the input bias current is reduced to 15uA. The LT3651-4.2 maximises battery life during all non-charging periods by draining <1uA from the battery. For safety and autonomous charge control, the device 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. The LT3651-4.2 is available in a low-profile (0.75mm) 36pin 5 x 6mm QFN package, and is offered in both E and I grade versions, guaranteed from -40 to 125^°C.