3.3V/2.5V Step-Up/Step-Down Charge Pump DC/DC Converter

The LTC3240-3.3/LTC3240-2.5 are step-up/step-down charge pump DC/DC converters that produce a fixed regulated output voltage of 3.3V or 2.5V over a wide input voltage range (1.8V to 5.5V).

With input voltages greater than the regulated output voltage the LTC3240 operates as a low dropout regulator. Once the input voltage drops within 100mV of the regulated output voltage the part automatically switches to step-up mode. In step-up mode the LTC3240 operates as a constant frequency (1.2MHz) doubling charge pump.

The LTC3240-3.3/LTC3240-2.5 feature low no load operating current (65µA typical) and ultralow operating current in shutdown (<1µA). Built-in soft-start circuitry prevents excessive inrush current during start-up. Thermal shutdown and current-limit circuitry allow the parts to survive a continuous short-circuit from VOUT to GND.

The LTC3240-3.3/LTC3240-2.5 require only three tiny external ceramic capacitors for an ultrasmall application footprint. The LTC3240-3.3/LTC3240-2.5 are available in a 6-pin (2mm × 2mm) DFN package.

Applications

* 2 AA to 2.5V

* 2-3 AA/Li-Ion to 3.3V

* Low Power Supplies for Cameras, I/O Supplies, Audio, PC Cards, Misc. Logic, etc., in a Wide Variety of Handheld Products

* Step-Up/Step-Down Charge Pumps Generate Fixed 3.3V or 2.5V Outputs

* VIN Range: 1.8V to 5.5V

* Output Current up to 150mA

* Automatic Mode Switching

* Constant Frequency (1.2MHz) Operation in Step-Up Mode

* Low Dropout Regulator Operation in Step-Down Mode

* Low No-Load Quiescent Current: IQ = 65µA

* Built-In Soft-Start Reduces Inrush Current

* Shutdown Disconnects Load from Input

* Shutdown Current < 1µA

* Short-Circuit/Thermal Protection

* Available in a 6-Lead (2mm × 2mm) DFN Package