Features
Inverts Input Voltage
Ultra-Low Voltage Ripple and 8 Typical Output Resistance with Two Flying Capacitors
Output Resistance of 18 Using One Flying Capacitor
210kHz (typ.) Switching Frequency
8-pin micro SMD Package (1.4mm × 1.4mm × 0.5mm)
Description The LM2781 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 LM2781 can provide up to 50mA of output current.
The LM2781 operates at a 210kHz typical switching frequency to minimize supply current (0.7mA 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 LM2781 is available in an 8-pin Micro SMD chip-scale package.
See also: LM2780, a slow clock (12kHz typ) version of this topology with extremely low supply current.
Applications
Cellular Phones
Pagers
PDAs
Op-Amp Power Supplies
Interface Power Supplies
Handheld Instruments
| 
