The LTC4020 from Linear Technology Corp. is an advanced 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 wide 4.5 V to 55 V input voltage range compatible with a variety of different input voltage sources. With an output voltage range up to 55 V and three selectable termination algorithms, the LTC4020 accommodates an equally wide variety of battery stack voltages and chemistries. The LTC4020 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 12 V to 24 V 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. Furthermore, 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, ideal 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.
Three pin-selectable charging profiles are optimized for various 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 CC/CV charging, as well as additional protection during battery preconditioning and absorption charging for lead-acid batteries. Two digital open-drain outputs provide charger status and signal fault conditions. These binary coded pins signal battery charging, standby or shutdown modes, battery temperature faults and bad battery faults. Other features of the battery charger include: temperature-qualified charging using an NTC thermistor, automatic recharge and precondition low current charging for deeply discharged cells.
The LTC4020 is housed in a low profile (0.75 mm) 38-pin 5 mm x 7mm QFN package with a backside metal pad for excellent thermal performance. The device is guaranteed for operation from -40 °C to 125 °C. 1,000-piece pricing starts at $4.95 each.
