Power Electronics

Charger/Buck Regulator Come in Tiny DFN

Linear Technology’s LTC3550 combines a dual input single-cell Li-Ion/Polymer battery charger and a high efficiency synchronous buck regulator in a 3-mm x 5-mm x 0.75-mm DFN package. The linear battery charger automatically selects the appropriate power source to efficiently charge batteries via a wall adapter up to 8 V (10 V absolute maximum) or a USB port. Operation is standalone.

Using a constant-current/constant-voltage algorithm, the charger can deliver up to 950 mA of charge current from a wall adapter supply, or up to 500 mA of charge current from a USB supply. The final float voltage accuracy is ±0.6%. The charger is equipped with a thermal regulation scheme that maximizes the charge rate. It draws less than 6 µA from the battery terminal in standby and 1 µA in shutdown mode.

The LTC3550's integrated synchronous buck regulator features an adjustable output voltage from 5.5 V to 0.6 V, delivering up to 600 mA of continuous output current. It uses internal switches with an RDS(ON) of only 0.40 Ω to deliver efficiencies as high as 96%. In addition, automatic Burst Mode operation optimizes efficiency at light loads, featuring a quiescent current of only 20 µA.

Using a constant-frequency current-mode architecture, the buck regulator operates from an input voltage range of 2.5 V to 5.5 V. Its switching frequency is 1.5-MHz. Pricing starts at $2 each for 1000-piece quantities.
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