Dual-Output Regulator Uses Switched-Capacitor Technique

A switched-capacitor doubler, a low dropout regulator, and a switched-capacitor inverter are all integrated in a low-profile, TSSOP-14 package in the LM2685 dual-output regulator. The device, which is designed for the portable communications market, provides +5V of regulated and -5V of unregulated power as required by components such as audio codecs, amplifiers and SIMMs. In addition, the -5V output can be used for contrast bias for LCDs and to increase the dynamic range of op amps used for analog inputs. By powering these functions, the LM2685 complements the main dc-to-dc converters in many portable systems, especially those that incorporate audio I/O and LCDs.The device’s input range is 2.85V to 5.5 V, matching voltages delivered by lithium ion batteries. It provides up to 50 mA of output current at +5V and 15 mA at -5V.