Intersil / Analog Devices / many · Integrated circuit

ICL7660 Charge Pump Inverter

Turns +5 V into -5 V with two capacitors and no inductor. The cheapest way to get a negative rail for an op-amp on a single-supply board.

Cheat sheet (SVG)

Logic level: 1.5-10 V
Package: PDIP-8 / SOIC-8

1.Pinout diagram

Highlight a signalhover to preview, click to keep

Pins 1-4

ICL7660

Pins 5-8

Pin detail

Hover a pin for its mappings and gotchas. Click to keep it here.

Logic level: 1.5-10 V
Package: PDIP-8 / SOIC-8

Fig. 1. ICL7660 Charge Pump Inverter, PDIP-8. Hover or tap a signal to light up every pin that carries it.

2.Watch out

Two 10 uF capacitors and nothing else: one across CAP+ and CAP-, one from VOUT to ground. No inductor, no layout drama.
Output current is only about 20 mA, and the output sags as you draw it because the pump has real output impedance. It is for biasing op-amps and comparators, not for powering anything.
Default oscillator runs around 10 kHz, which lands squarely in the audio band. In an audio circuit tie BOOST (pin 1) to V+ to push it to about 45 kHz, or hang a capacitor on OSC to move it deliberately.
LV (pin 6) should be grounded below 3.5 V supply and left open above it. Getting this backwards is the usual reason a 7660 works at 5 V and not at 3 V, or latches up at 9 V.
It can also double a voltage instead of inverting it, by rearranging the capacitors. The datasheet has the connection; it is not the default.
Absolute maximum is 10.5 V on the original ICL7660. The LM2662 and MAX1044 variants take more and deliver more current; check the exact part before applying 12 V.

3.Negative supply

What has to go around the chip before it will run.

Fig. 2. Negative supply, drawn from Table 1. Dashed parts are optional. Crossing wires are not connected.

Table 1. External parts, and why each one is there.
Part	Between	Why
10 uF	CAP+ (2) to CAP- (4)	The charge pump capacitor. This is the one that actually moves the charge across.
10 uF	VOUT (5) to GND	Reservoir on the output. Without it the negative rail is a sawtooth, not a supply.
Wire linkoptional	LV (6) to GND	LV bypasses the internal regulator below 3.5 V. Above 3.5 V it must be left open or the part can latch up.
100 nFoptional	V+ (8) to GND	Supply decoupling at the pin.

Output impedance is around 55 ohms, so the negative rail sags under load: at 20 mA you lose more than a volt. It is a bias supply for op-amps and LCD contrast, not a power rail.

4.Full pin reference

Every pin, alias and mapping. This is the table that prints.

Table 2. Pin assignments.

Complete pin reference for ICL7660 Charge Pump Inverter
Pin	Name	Also called	Functions	Notes
1	BOOST	NC on some parts	Oscillator boost	Tie to V+ to raise the oscillator to about 45 kHz, out of the audio band.
2	CAP+	-	Flying capacitor positive	10 uF between CAP+ and CAP-.
3	GND	-	Ground
4	CAP-	-	Flying capacitor negative
5	VOUT-V+ approx	-	Negative output	Roughly minus the supply, minus the droop under load. 10 uF to ground here.
6	LV	-	Low voltage select	Ground it below 3.5 V supply, leave open above. The wrong choice is why it works at one rail and not another.
7	OSCClock	-	Oscillator	A capacitor here slows the pump; an external clock overrides it.
8	V+1.5-10 V	-	Positive supply	10.5 V absolute maximum on the original part.

Primary sources

Analog Devices ICL7660 datasheet ↗

Found a wrong pin? The whole board is one file, data/boards/icl7660.json.

Edit this file on GitHub Report it instead