Features

• Low Noise Constant Frequency Charging of Two Series Supercapacitors
• Automatic Cell Balancing Prevents Capacitor Overvoltage During Charging
• Programmable Charge Current (Up to 150mA)
• Selectable 2.4V or 2.65V Regulation per Cell (LTC3225)
• Selectable 2V or 2.25V Regulation per Cell (LTC3225-1)
• Automatic Recharge
• I_VIN = 20μA in Standby Mode
• I_COUT < 1μA When Input Supply is Removed
• No Inductors
• Tiny Application Circuit (2mm × 3mm DFN Package, All Components <1mm High)

Typical Application

Description

The LTC3225/LTC3225-1 are programmable supercapacitor chargers designed to charge two supercapacitors in series to a selectable fixed output voltage (4.8V/5.3V for the LTC3225 and 4V/4.5V for the LTC3225-1) from input supplies as low as 2.8V to 5.5V. Automatic cell balancing prevents overvoltage damage to either supercapacitor. No balancing resistors are required.

Low input noise, low quiescent current and low external parts count (one flying capacitor, one bypass capacitor at V_IN and one programming resistor) make the LTC3225/ LTC3225-1 ideally suited for small battery-powered applications.

Charge current level is programmed with an external resistor. When the input supply is removed, the LTC3225/ LTC3225-1 automatically enter a low current state, drawing less than 1μA from the supercapacitors.

The LTC3225/LTC3225-1 are available in a 10-lead 2mm × 3mm DFN package.