High voltage inverting charge pumps offer low input and output ripple

May 09, 2012 // By Paul Buckley
Linear Technology Corporation has released two versatile high voltage charge pumps. The LTC3261 is a high voltage inverting charge pump that can deliver up to 100 mA of output current.

The LTC3260 has the same charge pump as the LTC3261, but also includes both positive and negative LDO regulators that can source up to 50 mA output current each.      

The negative LDO post regulator is powered from the inverting charge pump output.      

The positive and negative LDO output voltages can be adjusted down to 1.2 V and -1.2 V, respectively using external resistor dividers. Both devices operate over a wide 4.5 V to 32 V input voltage range.     

The internal charge pump of the LTC3260 and LTC3261 function in either low quiescent current Burst Mode operation or low noise constant frequency mode at up to 88% efficiency. In Burst Mode operation the charge pump output regulates to –0.94 V IN.

Also, in Burst Mode operation the LTC3261 draws only 60 μA of quiescent current, while the LTC3260 draws 100 μA with both LDOs enabled. Constant frequency operation offers low input and output ripple; in this mode the charge pump produces an output equal to –V IN and operates at a fixed 500 kHz or to a programmed value between 50 kHz to 500 kHz using an external resistor.      

Other IC features include low external parts count with ceramic capacitor stability, soft-start circuitry to prevent excessive current flow during start-up, plus short circuit and thermal protection.

The LTC3260 and LTC3261 are well-suited for a variety of applications such as low noise bipolar/inverting supplies from a high voltage input, industrial/instrumentation low noise bias generators, portable medical equipment and automotive infotainment systems.     

Availability and Pricing      

The LTC3260 is available in a low-profile (0.75 mm) 3 mm x 4 mm 14-lead DFN package and a 16-lead MSOP package, both with a backside thermal pad. The LTC3261 is available in a 12-lead MSOP package with backside thermal pad. For both devices, the E- and I-grade operating junction temperature is -40 to +125°C. 1000-piece pricing for the E grade