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Breakthrough 2A Solar Battery Charger Matches Peak Power Tracking with Simple Control Loop

26th April 2010

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Linear Technology has introduced the LT3652, an innovative, solar power directed monolithic buck battery charger IC for modern battery chemistries. 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. 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.

The LT3652 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 optimized 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%. Once 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.