LM2664M6/NOPB

The LM2664M6/NOPB from Texas Instruments is a CMOS charge-pump voltage converter that inverts a positive input voltage in the range of 1.8V to 5.5V to the corresponding negative voltage (-1.8V to -5.5V). Using only two low-cost external capacitors, it provides up to 40mA output current with 91% typical conversion efficiency. The 160kHz oscillator frequency reduces output resistance and voltage ripple. With 220μA operating current and 1μA shutdown current, the device is optimized for battery-powered systems requiring a negative rail from a single positive supply.

The LM2664 uses a switched-capacitor charge-pump circuit with two phases. During Phase 1 (charge), the internal flying capacitor (CP) is connected between VIN and GND, charging it to the input voltage. During Phase 2 (transfer), the flying capacitor is reconnected with its positive terminal to GND and its negative terminal to the output, transferring the stored charge to the output capacitor (CO) and generating a negative voltage at the OUT pin. The internal MOSFET switches alternate between these two phases at 80kHz (160kHz oscillator, divide-by-2), creating an inverted output voltage approximately equal to -VIN. The 12Ω output impedance results from the combined on-resistance of the internal switches and the ESR of the external capacitors. The SD pin disables the oscillator and reduces current to 1μA in shutdown mode.

• Negative rail generation for dual-supply op-amps from single battery
• Cell phone LCD bias voltage inverter
• Portable instrument negative reference for ADC/DAC
• GAAS FET gate bias from single positive supply
• RS-232 negative supply generation from 3.3V or 5V