Datasheet

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LM2664
www.ti.com SNVS005D –NOVEMBER 1999–REVISED MAY 2013
CONNECTION DIAGRAMS
6-Pin Small Outline Package
Figure 13. DBV Package Top View Figure 14. Actual Size
Pin Descriptions
Pin Name Function
1 GND Power supply ground input.
2 OUT Negative voltage output.
3 CAP− Connect this pin to the negative terminal of the charge-pump capacitor.
4 SD Shutdown control pin, tie this pin to V+ in normal operation, and to GND for shutdown.
5 V+ Power supply positive voltage input.
6 CAP+ Connect this pin to the positive terminal of the charge-pump capacitor.
Circuit Description
The LM2664 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 15 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; at the same time, 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+) when there is no load current. The
output voltage drop when a load is added is determined by the parasitic resistance (R
ds(on)
of the MOSFET
switches and the ESR of the capacitors) and the charge transfer loss between capacitors. Details will be
discussed in the following application information section.
Figure 15. Voltage Inverting Principle
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