55 VIN/55 VOUT buck-boost battery charging controller

November 06, 2013 // By Graham Prophet
LTC4020 is a high voltage power manager and multi-chemistry battery charger designed to efficiently transfer power from a variety of sources to a system power supply rail and a battery.

The device offers precision charge current regulation, ±0.5% charge voltage regulation and operates across a 4.5V to 55V input voltage range compatible with a variety of different input voltage sources. With an output voltage range up to 55V and three selectable termination algorithms, the LTC4020 accommodates a wide variety of battery stack voltages and chemistries. It contains a step-up/step-down DC/DC controller, enabling operation with battery voltages that are above, below or equal to the input voltage (VIN). Typical applications include portable industrial and medical equipment, solar-powered systems, military communications equipment, plus 12V to 24V embedded automotive systems.

The LTC4020 features an intelligent PowerPath topology that reduces the voltage range required by downstream system components to that of the expected battery voltage range rather than the full extent of the input voltage source. However, instant-on operation still ensures system load power with a fully discharged battery. This topology preferentially provides power to the system load when input power is limited - the device’s ideal-diode controller guarantees that ample power is always available to VOUT if there is insufficient power available from the DC/DC converter. A maximum power point control (MPPC) circuit features an input voltage regulation loop, which controls charge current to hold the input voltage at a programmed level, for high impedance input or solar panel-powered applications. When no input supply is present, the battery drain current is reduced to only 10µA, maintaining maximum stored capacity.

The LTC4020’s three pin-selectable charging profiles are optimised for a variety of battery chemistries. The LTC4020 can provide a constant-current/constant-voltage (CC/CV) charge characteristic with either C/10 or timed termination for use with lithium-based battery systems including Li-Ion, Li-polymer and LiFePO4. A constant-current (CC) characteristic with timed termination can be used for charging supercapacitors or trickle charging nickel-based batteries. Finally, a 4-step, 3-stage lead-acid charge profile works well with all types of lead-acid batteries including sealed, AGM and flooded. An integrated timer controls termination during