SNVS002D – JANUARY 1999 – REVISED MAY 2013
Pin Descriptions
Pin
1
Name
Voltage Inverter
FC
(LM2662)
Frequency control for internal oscillator:
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
2
3
4
5
6
SD
(LM2663)
CAP+
GND
CAP−
OUT
LV
Shutdown control pin, tie this pin to the ground in normal
operation.
Connect this pin to the positive terminal of charge-pump
capacitor.
Power supply ground input.
Connect this pin to the negative terminal of charge-pump
capacitor.
Negative voltage output.
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.
Same as inverter.
Same as inverter.
Power supply positive voltage input.
Same as inverter.
Power supply ground input.
LV must be tied to OUT.
Same as inverter.
Function
Voltage Doubler
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.
Power supply positive voltage input.
Positive voltage output.
8
V+
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.
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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