The MAX1673 charge-pump inverter provides a low-cost, compact means of generating a regulated negative output from a positive input at up to 125mA. It requires only three small capacitors, and only two resistors to set its output voltage. The input range is 2V to 5.5V. The regulated output can be set from 0V to -VIN in Skip regulation mode or -1.5V to -VIN in Linear (LIN) regulation mode.

In Skip mode, the MAX1673 regulates by varying its switching frequency as a function of load current. This On-Demand™ switching gives the MAX1673 two advantages: very small capacitors and very low quiescent supply current. At heavy loads, it transfers energy from the input to the output by switching at up to 350kHz. It switches more slowly at light loads, using only 35µA quiescent supply current.

In Linear mode, the MAX1673 switches at a constant 350kHz at all loads and regulates by controlling the current-path resistance. This provides constant-frequency ripple, which is easily filtered for low-noise applications.

This device also features a 1µA logic-controlled shutdown mode and is available in a standard 8-pin SO package. For a device that delivers about 10mA and fits in a smaller package, refer to the MAX868.