LTC1429

Regulated Negative Voltage from a SinglePositive Supply
External Clock for Synchronization in NoiseSensitive Systems
REG Output Indicates Output is in Regulation
Low Output Ripple: 5mV Typ
Can Provide Regulated 5V from a 3V Supply
Supply Current: 600µA Typ
Shutdown Mode Drops Supply Current to 0.2µA
Up to 12mA Output Current
Adjustable or Fixed Output Voltages
Requires Only Three or Four External Caps
Output Regulation: 5%
n Available in SO-8 Packages

The LTC^®1429 is a switched-capacitor voltage inverter de-signed to provide a regulated negative voltage from a singlepositive supply and permits clock synchronization in noisesensitive systems. The LTC1429CS operates from a single 3Vto 8V supply and provides an adjustable output voltage from1.25V to 8V. An on-chip resistor string allows theLTC1429CS to be configured for output voltages of 3.5V,4V, 4.5V or 5V. The LTC1429CS8 is optimized forapplications which require a fixed 4V output from a 5Vsupply and requires only a single external 0.1µF flyingcapacitor. The LTC1429CS requires one or two external0.1µF capacitors, depending on input voltage. Both versionsrequire additional external input and output bypass capaci-tors. An optional compensation capacitor at ADJ/COMP canbe used to reduce the output voltage ripple.

Each version of the LTC1429 guarantees output regulation of5%. The device includes an open-drain REG output whichpulls low when the output is within 5% of the set value. Outputripple is typically as low as 5mV. The LTC1429 requires anexternal clock applied to the SYNC/SD for normal operationand consumes a typical quiescent current of 600µA. Holdingthe SYNC/SD either high or low brings the device intoshutdown and the supply current drops to 0.2µA. For appli-cations which don't have a clock signal available, the LTC1261provides the same functionality with an internal oscillator. Forapplications which require output ripple below 1mV, see theLTC1550/LTC1551. The device is available in a 14-pinSO package and the LTC1429CS8 is available in an 8-pin SOpackage