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1046

"Inductorless" +5V to -5V Converter

Linear Technology 

LTC1046

TYPICAL APPLICATI S

Battery Splitter

A common need in many systems is to obtain positive and

negative supplies from a single battery or single power

supply system. Where current requirements are small, the

circuit shown in Figure 10 is a simple solution. It provides

symmetrical positive or negative output voltages, both

VB

9V

C1 +

10µF

LTC1046

1

BOOST

V+ 8

2 CAP + OSC 7

3

GND

LV 6

4 CAP – VOUT 5

3V ≤ VB ≤ 12V

+VB/2

4.5V

REQUIRED FOR VB < 6V

–VB/2

–4.5V

C2

10µF

OUTPUT COMM0N

1046 F10

Figure 10. Battery Splitter

equal to one half the input voltage. The output voltages are

both referenced to Pin 3 (output common). If the input

voltage between Pin 8 and Pin 5 is less than 6V, Pin 6

should also be connected to Pin 3, as shown by the

dashed line.

Paralleling for Lower Output Resistance

Additional flexibility of the LTC1046 is shown in Figures 11

and 12. Figure 11 shows two LTC1046s connected in

parallel to provide a lower effective output resistance. If,

however, the output resistance is dominated by 1/fC1,

increasing the capacitor size (C1) or increasing the fre-

quency will be of more benefit than the paralleling

circuit shown.

Figure 12 makes use of “stacking” two LTC1046s to

provide even higher voltages. In Figure 12, a negative

voltage doubler or tripler can be achieved depending upon

how Pin 8 of the second LTC1046 is connected, as shown

schematically by the switch.

+

C1

10µF

LTC1046

1

BOOST

2 CAP +

3

GND

V+ 8

OSC 7

LV 6

4 CAP – VOUT 5

+

C1

10µF

LTC1046

1

BOOST

2 CAP +

3

GND

V+ 8

OSC 7

LV 6

4 CAP – VOUT 5

1/4 CD4077

V+

VOUT = –(V+)

C2

20µF

OPTIONAL SYNCHRONIZATION

CIRCUIT TO MINIMIZE RIPPLE

1046 F11

Figure 11. Paralleling for 100mA Load Current

8

+

10µF

V+

LTC1046

1

BOOST

2 CAP +

3

GND

4 CAP –

V+ 8

OSC 7

LV 6

VOUT 5

C1

10µF

–(V+)

10µF

FOR VOUT = –3V+

LTC1046

1

BOOST

V+ 8

2 CAP + OSC 7

3

GND

LV 6

4 CAP – VOUT 5

Figure 12. Stacking for Higher Voltage

FOR VOUT = –2V+

VOUT

10µF

1046 F12

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