The MAX868 inverting charge pump provides a low-cost and compact means of generating a regulated negative voltage up to -2 x V IN from a positive input voltage between 1.8V and 5.5V. It uses a pulse-frequencymodulation (PFM) control scheme to generate the regulated negative output voltage. PFM operation is obtained by gating the internal 450kHz oscillator on and off as needed to maintain output voltage regulation. This unique on-demand switching scheme gives the MAX868 excellent light-load efficiency without degrading its fullload operation (up to 30mA), permitting smaller capacitors to take advantage of the oscillator's high switching frequency.