Charging Controller Serves Solar Applications
December 9, 2013. Linear Technology has announced the LT8490, a synchronous buck-boost battery charging controller for lead-acid and lithium batteries, featuring automatic maximum power point tracking (MPPT) and temperature compensation. The device operates from input voltages above, below, or equal to the regulated battery float voltage. The LT8490’s full-featured battery charger offers many selectable constant-current constant-voltage (CC-CV) charging profiles, making it suitable for charging a variety of lithium or lead acid chemistry types, including sealed-lead acid, gel cells, and flooded cells. All charge termination algorithms are provided onboard, eliminating the need for software or firmware and thus reducing design cycle time.
The LT8490 operates over a 6-V to 80-V input voltage range and can produce a 1.3-V to 80-V battery float voltage output using a single inductor with 4-switch synchronous rectification. The device is capable of charging currents as high as 10 A depending on the choice of external FETs. The LT8490’s MPPT circuit enables a sweep of the full operating range of a solar panel, finding the true maximum power point, even in the presence of local maxima points caused by partial shading of the panel. Once the true maximum power point is found, the LT8490 will operate at that point while using a dithering technique to quickly track changes in the local maximum power point. With this methodology, the LT8490 fully utilizes the power generated by a solar panel even in non ideal operating environments.
The LT8490 performs automatic temperature compensation of the battery charge voltage by sensing an external thermistor on the battery. The STATUS and FAULT pins can be used to drive LED indicator lamps. Charging current limits can be adjusted by changing as few as 1 or 2 resistors, and a charging time scale can be selected with the appropriate resistor divider. Other features of the device include: input and charge current limit pins, a 3.3V regulated LDO output, status pins and a synchronizable fixed switching frequency.
The LT8490 is available in a low-profile (0.75-mm) 64-pin 7-mm x 11-mm QFN package. The device is offered in both E and I grades, which are guaranteed for operation from -40°C to 125°C. 1,000-piece pricing for the E grade starts at $10.35 each.