SP6660EB datasheet(12/22 Pages) SIPEX

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SP6660DS/11

SP6660 200mA Charge Pump Inverter or Doubler

THEORY OF OPERATION

Negative Voltage Inverter

This is the most common application of the

SP6660 where a +1.5V to +4.25V input is

converted to a -1.5V to -4.25V output. In the

inverting mode, the SP6660 is typically operated

with LV connected to GND. Since the LV may

be left open, the substitution of the SP6660 for

the ICL7660 industry standard is simplified.

The circuit for the voltage inverter mode can be

found in Figure 21. This operating circuit uses

only two external capacitors, C1 and C2, for

the internal charge pump. This allows designers

to avoid any EMI concerns with the costly,

space-consuming inductors typically used with

switching regulators.

Figure 21. Typical Operating Circuit for the Voltage Inverter

OSC

OUT

SP6660

+VIN

+1.5V to +4.25V

µF to 150µF

CAP+

CAP-

GND

NEGATIVE

VOLTAGE

OUTPUT

TYPICAL CIRCUIT: VOLTAGE INVERTER

The SP6660 is insensitive to load current

changes. Output Source Resistance vs. Supply

Voltage and Temperature curves are shown in

Figures 14 to 16. A typical output source

resistance of 5.2

Ω allows an output voltage of

-4.25V under light load with an input of +4.25V.

This output voltage decreases to only -4.0V

with a load current draw of 100mA.

The peak-to-peak output ripple voltage is

calculated as follows:

VRIPPLE =

+ IOUT(ESRC2)

IOUT

2(fPUMP)(C2)

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