The LT8491 charge controller from Analog Devices is an innovative buck-boost switching regulator battery charger that implements a constant-current constant-voltage (CCCV) charging profile that can be used for most battery types, including sealed lead-acid (SLA), flooded, gel and lithium-ion.
LT8491 Application Circuit
The LT8491 device can operate from input voltages above, below or equal to the output voltage and can be powered by a solar panel or a DC power supply. Integrated on-chip logic provides automatic true power point tracking (MPPT) for solar powered applications. The MPPT function not only continuously tracks the maximum power point, but also periodically sweeps the input panel voltage in order to select the correct maximum on the power curve. In doing so, an increase in power harvested from the panel during partial shade conditions is possible when multiple peaks occur on the power curve. During periods of low light, a low power mode allows the charger to deliver a small charge current even if there is not enough light for the MPPT function to operate.
LT8491 MPPT Performance Graph
The LT8491 can perform automatic temperature compensation by sensing an external thermistor thermally coupled to the battery. The STATUS pin can be used to drive an LED indicator lamp. The device is available in a low profile (0.75mm) 7mm × 11mm 64-lead QFN package and is specified for operation over the temperature range -40°C to +125°C.
Demo Board
The LT8491 is supported by the DC2703A-A-KIT which contains the DC2703A (LT8491 demo board) and DC1613A (USB-to-I2C controller). Together they provide a high performance buck-boost battery charger converter with an I2C interface. The LT8491 implements a maximum power point tracking (MPPT) function and flexible charging profiles, suitable for most battery types such as flooded and sealed lead acid batteries and Li-Ion batteries. A Microsoft Windows-Based GUI (Graphical User Interface) application called “simpleLT8491” is also provided.
The DC2703A-A-KIT demo board is configured for 17V to 54V input voltage range and the power source can be a solar panel with 36 to 72 cells (up to 200W) or a DC voltage source. Two input connectors are provided and an ideal diode controller LTC4359 protects the DC power supply output from being back fed from the solar panel. This allows, for example, a 24VDC supply to be plugged in while a solar panel with higher voltage is being used to power the circuit. The DC2703A-A-KIT demo board output is set up for charging a 12V SLA battery with up to 16.6A charge current. The DC2703A-A-KIT demo board can be modified to support much higher output voltage, with modifications including higher voltage rating output side MOSFETs and capacitors.
The LT8491 includes a slave I2C compatible interface for digital control of the charger settings and digital readouts of charger telemetry and status. The Microsoft Windows- Based GUI (Graphical User Interface) application provided for this demo board makes it very easy to read charger telemetry and status data, as well as the ability to change the charging algorithm by writing to the appropriate configuration registers. The LT8491 EEPROM on the DC2703A-A-KIT demo board is programmed with the onboard resistor values to accurately read charger telemetry and status registers data.
An RJ25 modular jack on the demo board can be used to connect an external NTC temperature sensor mounted at the battery. This allows temperature compensation of the charge voltage, which is important for lead acid batteries. The same connector can be used for remote sensing of battery voltage, to compensate for voltage drops in long battery cables. The onboard LED displays the charge state.
Anglia are offering customers a FREE Demo board and samples of the LT8491 high voltage buck-boost battery charge controller from Analog Devices, please fill in the form below to register your interest now.
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