EL7584 datasheet(11/16 Pages) RENESAS

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EL7584

FN7317 Rev 2.00

Page 11 of 16

February 4, 2005

Single Stage Charge Pump

Positive Charge Pump Design Considerations

A single stage charge pump is shown above. The maximum

VON output voltage is determined by the following equation:

where:

•RONN and RONP resistance values depend on the VDDP

voltage levels. For 12V supply, RON is typically 33. For

6V supply, RON is typically 45.

If additional stage is required, the LX switching signal is

recommended to drive the additional charge pump diodes.

The drive impedance at the LX switching is typically 150m

.

The figure below illustrates an implementation for two-stage

positive charge pump circuit.

OSC

R21

R22

VREF

3.3µF

0.1µF

5V TO

17V

VDDN

DRVN

VSSN

VDDP

DRVP

VSSP

FBP

FBN

VFBP

R11

R12

2.2µF

0.1µF

5V TO

17V

VOFF

VON

RON IS 30 - 40 FOR VDD 6V TO 12V

RONP

RONN

RONP

RONN

COUT2

CCPN

CCPP

COUT1

VON max

 2V

DDCPP - IOUT

2RONN



RONP - 2 VDIODE - IOUT

0.5 FS CCPP



--------------------------------------------



- IOUT

0.5 FS COUT1



------------------------------------------------





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