LTC4425 linear supercap charger

The LTC4425 IC is a constant-current/constant-voltage linear charger designed to charge a 2-cell supercap stack from a Li-Ion/Polymer battery, USB port or a 2.7V to 5.5V current-limited supply.

The LTC4425 operates as an ideal diode with an low resistance (  50mΩ on ) making it suitable for high peak-power/low average power applications.

The LTC4425 charges the output capacitors to an externally programmed output voltage in LDO mode at a constant charge current, or to VIN in normal mode with a smart charge current profile to limit the inrush current until the VIN to VOUT differential is less than 250mV.

The charge current (VOUT current limit) can be programmed by connecting a resistor between PROG and GND.

An internal balancing circuit maintains equal voltages across each supercapacitor and clamps the peak voltage across each .

Main features of the LTC4425 linear supercap charger are :

-monitor 50mΩ ideal diode from VIN to VOUT

-smart charge current profile limits inrush current

- internal cell balancer (No External Resistors)

-programmable output voltage (LDO Mode)

-programmable VIN to VOUT current limit

-continuous monitoring of VIN to VOUT current via PROG Pin

-low quiescent current: 20μA

-VIN Power Fail, PGOOD Indicator

-2.45V/2.7V Cell Protection Shunts (4.9V/5.4V SuperCap Max Top-Off Voltage)

-3A Peak Current Limit, Thermal Limiting