LM2662 datasheet(6/12 Pages) NSC

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Connection Diagrams

Pin Description

Name

Function

Voltage Inverter

Voltage Doubler

Frequency control for internal oscillator:

Same as inverter.

(LM2662)

FC = open, f

OSC = 20 kHz (typ);

FC = V+, f

OSC = 150 kHz (typ);

FC has no effect when OSC pin is driven

externally.

1SD

(LM2663)

Shutdown control pin, tie this pin to the ground

in normal operation.

Same as inverter.

CAP+

Connect this pin to the positive terminal of

charge-pump capacitor.

Same as inverter.

GND

Power supply ground input.

Power supply positive voltage input.

CAP−

Connect this pin to the negative terminal of

charge-pump capacitor.

Same as inverter.

OUT

Negative voltage output.

Power supply ground input.

Low-voltage operation input. Tie LV to GND

when input voltage is less than 3.5V. Above

3.5V, LV can be connected to GND or left

open. When driving OSC with an external clock,

LV must be connected to GND.

LV must be tied to OUT.

OSC

Oscillator control input. OSC is connected to an

internal 15 pF capacitor. An external capacitor

can be connected to slow the oscillator. Also,

an external clock can be used to drive OSC.

Same as inverter except that OSC cannot be

driven by an external clock.

V+

Power supply positive voltage input.

Positive voltage output.

Circuit Description

The LM2662/LM2663 contains four large CMOS switches

which are switched in a sequence to invert the input supply

voltage. Energy transfer and storage are provided by exter-

nal capacitors.

Figure 2 illustrates the voltage conversion

scheme. When S

1 and S3 are closed, C1 charges to the sup-

ply voltage V+. During this time interval switches S

2 and S4

are open. In the second time interval, S

1 and S3 are open

and S

2 and S4 are closed, C1 is charging C2. After a number

of cycles, the voltage across C

2 will be pumped to V+. Since

the anode of C

2 is connected to ground, the output at the

cathode of C

2 equals −(V+) assuming no load on C2, no loss

in the switches, and no ESR in the capacitors. In reality, the

charge transfer efficiency depends on the switching fre-

quency, the on-resistance of the switches, and the ESR of

the capacitors.

8-Lead SO (M)

DS100003-20

DS100003-21

Top View

Order Number LM2662M, LM2663M

See NS Package Number M08A

DS100003-22

FIGURE 2. Voltage Inverting Principle

LM2662 Datasheet(PDF) 6 Page - National Semiconductor (TI)

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