SP6660EB datasheet(13/22 Pages) EXAR

13 / 22 page

SP6660DS/11

SP6660 200mA Charge Pump Inverter or Doubler

For a nominal f

PUMP of 5kHz (where fOSC =10kHz)

and C2=150

µF with an ESR of 0.2Ω, the ripple

is approximately 90mV with a 100mA load

current. If C2 is raised to 390

µF, the ripple drops

to 45mV. The output ripple voltage is calculated

by noting that capacitor C2 supplies the output

current during one-half of the charge pump cycle.

OSC is internally connected to a 15pF capacitor.

An external capacitor can be added to slow the

oscillator. Designers should take care to

minimize stray capacitance. An external

oscillator may also be connected to overdrive

OSC. Refer to the Oscillator Control section

for further details.

Figure 22. Typical Operating Circuit for the Positive Voltage Doubler

OSC

OUT

SP6660

+VIN

+1.5V to +4.25V

µF to 150µF

CAP+

CAP-

GND

DOUBLE

VOLTAGE

OUTPUT

TYPICAL CIRCUIT: VOLTAGE DOUBLER

Positive Voltage Doubler

The SP6660 can double the output voltage of an

input power supply or battery. From a +4.25V

input, the circuit in Figure 22 can provide 100mA

with +8.0V at V+. The no-load voltage output at

V+ is 2(V

INL).

LV may be tied to OUT pin for all input voltages

in the positive voltage doubler mode. Connect

the power-supply positive voltage input to GND

pin. Connect the power-supply ground input to

OUT pin. V+ is the positive voltage output in

this mode.

Designers may overdrive OSC in the positive

voltage doubler mode. Refer to the Oscillator

Control section for further details.

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