4-17

TELCOM SEMICONDUCTOR, INC.

7

6

5

4

3

1

2

8

TCM680

+5V TO

C1, C2 (

0.1

1089

0.47

339

1

232

3.3

165

4.7

157

10

146

22

141

100

137

C3, C4 (

0.47

1540

1

734

3.3

236

4.7

172

10

91

22

52

100

27

Paralleling Devices

Paralleling multiple TCM680s reduces the output resis-

tance of both the positive and negative converters. The

effective output resistance is the output resistance of a

single device divided by the number of devices. As illus-

trated in Figure 7, each requires separate pump capacitors

capacitors.

3V Battery

Figure 8 shows a complete

±5V power supply using one

3V battery. The TCM680 provides +6V at V

+

regulated to +5V by the TC55, and –5V by the negative LDO.

The input to the TCM680 can vary from 3V to 6V without

affecting regulation appreciably. With higher input voltage,

more current can be drawn from the outputs of the TCM680.

outputs simultaneously. Assuming 150

Ω source resistance

for both converters, with (I

+

pump will droop 3V, providing +7V for the negative charge

pump.

V

OUT

V

OUT

C

OUT

V

IN

V

IN

V

IN

GND

GND

10

µF

10

µF

22

µF

10

µF

10

µF

NEGATIVE

SUPPLY

TCM680

TCM680

GND

+

–

+

–

+

–

+

–

+

–

+

+

–

–

+

–

–

–

–

+

–

Figure 7. Paralleling TCM680 for Lower Output Source Resistance