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Features
Inverts Input Voltage
Ultra-Low Voltage Ripple and 8Ω Typical Output Resistance with Two Flying Capacitors
Output Resistance of 18Ω Using One Flying Capacitor
12kHz (typ.) Switching Frequency
8-pin micro SMD Package (1.4mm × 1.4mm × 0.5mm)
Description The LM2780 is a charge pump that inverts an input voltage in the range of 1.8V to 5.5V to the corresponding output voltage
of -1.8V to -5.5V. With use of three or four low-cost external ceramic capacitors, the LM2780 can provide up to 50mA of output
current.
The LM2780 operates at a 12kHz typical switching frequency to minimize supply current (60µA typ.). Two charge pumps operate
180° out of phase to significantly reduce the output voltage ripple compared to that of traditional single-phase charge pump
circuits. If larger output ripple can be tolerated, optional capacitor C2 may be omitted to reduce the cost and size of the
solution. The LM2780 is available in an 8-pin Micro SMD chip-scale package.
See also: LM2781, a fast clock (210kHz typ) version of this topology with even lower output voltage ripple.
Applications
Cellular Phones
Pagers
PDAs
Op-Amp Power Supplies
Interface Power Supplies
Handheld Instruments
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