Datasheet

LM2662, LM2663
www.ti.com SNVS002D –JANUARY 1999–REVISED MAY 2013
Pin Descriptions
Pin Name Function
Voltage Inverter Voltage Doubler
1 FC 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.
1 SD Shutdown control pin, tie this pin to the ground in normal Same as inverter.
(LM2663) operation.
2 CAP+ Connect this pin to the positive terminal of charge-pump Same as inverter.
capacitor.
3 GND Power supply ground input. Power supply positive voltage input.
4 CAP− Connect this pin to the negative terminal of charge-pump Same as inverter.
capacitor.
5 OUT Negative voltage output. Power supply ground input.
6 LV Low-voltage operation input. Tie LV to GND when input LV must be tied to OUT.
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.
7 OSC Oscillator control input. OSC is connected to an internal Same as inverter except that OSC cannot be driven by
15 pF capacitor. An external capacitor can be connected an external clock.
to slow the oscillator. Also, an external clock can be used
to drive OSC.
8 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 external capacitors. Figure 18 illustrates the voltage
conversion scheme. When S
1
and S
3
are closed, C
1
charges to the supply voltage V+. During this time interval
switches S
2
and S
4
are open. In the second time interval, S
1
and S
3
are open and S
2
and S
4
are closed, C
1
is
charging C
2
. 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 C
2
, no loss in the
switches, and no ESR in the capacitors. In reality, the charge transfer efficiency depends on the switching
frequency, the on-resistance of the switches, and the ESR of the capacitors.
Figure 18. Voltage Inverting Principle
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