Solar charger
01 September 2009
Linear Technology has launched the LT3652; a solar power directed monolithic buck battery charger IC.
The LT3652 features an innovative input voltage regulation loop, which controls charge current to hold the input voltage at a programmed level. When the LT3652 is connected to a solar panel, the input regulation loop maintains the panel at peak output power.
It accepts a wide range of inputs from 4.95V to 32V with a 40V absolute maximum rating for added system margin. The input voltage regulation loop also allows optimised charging from poorly regulated sources where the input can collapse under overcurrent conditions. It charges a variety of battery pack configurations, including 1 to 3 Li-Ion / Polymer cells in series, 1 to 4 LiFePO4 (Lithium Iron Phosphate) cells in series and sealed lead acid (SLA) batteries up to 14.4V. Applications include solar powered systems, 12V to 24V automotive equipment and battery chargers. The LT3652’s charge current is programmable up to 2A. This stand-alone battery charger requires no external microcontroller, and features user-selectable termination, including C/10 or an onboard timer. The device’s 1MHz fixed switching frequency enables small solution sizes.
Float voltage feedback accuracy is specified at 0.5%, charge current accuracy is 5% and C/10 detection accuracy is ±2.5%. When charging is terminated, the LT3652 automatically enters a low current standby mode, which reduces the input supply current to 85uA. In shutdown, the input bias current is reduced to 15uA. For autonomous charge control, an auto-recharge feature starts a new charging cycle if the battery voltage falls 2.5% below the programmed float voltage.
The LT3652 is available in a low-profile (0.75mm) 12-pin 3mm x 3mm DFN package, and is offered in both E and I grade versions, guaranteed from –40C to 125C.
According to Steve Pietkiewicz, Vice President and General Manager of Power Products, “The LT3652’s simple but unique input voltage regulation loop circuitry delivers virtually the same charging efficiency as more complex and expensive Maximum Peak Power Tracking (MPPT) techniques.”
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