Linear Technology describes its LT3652 as an innovative, solar-power-directed monolithic buck battery-charger IC for modern battery chemistries. An input-voltage-regulation loop controls the charge current to hold the input voltage at a programmed level. When connected to a solar panel, the input-regulation loop maintains the panel at peak output power. According to the company, the loop's circuitry delivers virtually the same charging efficiency as more complex and expensive maximum-peak-power-tracking techniques. The IC accepts inputs from 4.95 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 one to three Li-Ion/polymer cells in series, one to four LiFePO4 (lithium-iron-phosphate) cells in series and sealed lead acid batteries up to 14.4V. Applications include solar-powered systems, 12 to 24V automotive equipment and battery chargers. The 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 IC automatically enters a low-current standby mode, which reduces the input supply current to 85µA. In shutdown, the input bias current is reduced to 15µA. 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.
