Datasheet

LM2681

SNVS042B –MARCH 1999–REVISED MAY 2013

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CONNECTION DIAGRAM

Figure 10. SOT-23, 6-Lead Package – Top View Figure 11. Actual Size

See Package Number DBV

PIN DESCRIPTION

Function

Pin Name

Voltage Doubler Voltage Split

1 V+ Power supply positive voltage input Positive voltage output

2 GND Power supply ground input Same as doubler

3 CAP− Connect this pin to the negative terminal of the charge- Same as doubler

pump capacitor

4 GND Power supply ground input Same as doubler

5 OUT Positive voltage output Power supply positive voltage input

6 CAP+ Connect this pin to the positive terminal of the charge-pump Same as doubler

capacitor

Circuit Description

The LM2681 contains four large CMOS switches which are switched in a sequence to double the input supply

voltage. Energy transfer and storage are provided by external capacitors. Figure 12 illustrates the voltage

conversion scheme. When S

and S

are closed, C

charges to the supply voltage V+. During this time interval,

switches S

and S

are open. In the next time interval, S

and S

are open; at the same time, S

and S

are

closed, the sum of the input voltage V+ and the voltage across C

gives the 2V+ output voltage when there is no

load. 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 APPLICATION INFORMATION section.

Figure 12. Voltage Doubling Principle

Product Folder Links: LM2681