+5V TO ±10V VOLTAGE CONVERTER
1
2
3
4
5
6
7
8
TCM680
Table 1. ROUT vs. C1 ,C2
Paralleling Devices
C1, C2 (µF)
ROUT (Ω)
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
C1 and C2, but all can share a single set of reservoir
capacitors.
0.1
0.47
1
1089
339
232
165
157
146
141
137
3.3
4.7
10
±5V Regulated Supplies From A Single
22
3V Battery
100
Figure 8 shows a complete ±5V power supply using one
3V battery. The TCM680 provides +6V at V+OUT, which is
regulatedto+5VbytheTC55,and–5VbythenegativeLDO.
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.
With 5V at VIN, 10mA can be drawn from both regulated
outputs simultaneously. Assuming 150Ω source resistance
forbothconverters, with(I+L +IL)=20mA, thepositivecharge
pump will droop 3V, providing +7V for the negative charge
pump.
Table 2. VRIPPLE (p-p) vs. C3, C4 (IOUT = 10mA)
C3, C4 (µF)
VRIPPLE (mV)
0.47
1
1540
734
236
172
91
3.3
4.7
10
22
52
100
27
VIN
VIN
+
+
VIN
C1
C1
+
+
–
10µF
10µF
10µF
–
–
–
C1
C1
TCM680
TCM680
GND
+
+
C2
–
C2
VOUT
+
–
+
–
–
NEGATIVE
SUPPLY
10µF
VOUT
–
–
C2
C2
GND
–
+
–
COUT
22µF
GND
Figure 7. Paralleling TCM680 for Lower Output Source Resistance
TELCOM SEMICONDUCTOR, INC.
4-17
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
