CHARGE PUMP DC-TO-DC
VOLTAGE CONVERTER
TC7660
VOUT = –V–
1
2
C1
10µF
+
3
4
8
7
1 MΩ
+
10µF
TC7660
6
5
V– INPUT
Figure 10. Positive Voltage Conversion
Voltage Splitting
The same bidirectional characteristics used in Figure 10
can also be used to split a higher supply in half, as shown in
Figure 11. The combined load will be evenly shared be-
tween the two sides. Once again, a high value resistor to the
LV pin ensures start-up. Because the switches share the
load in parallel, the output impedance is much lower than in
the standard circuits, and higher currents can be drawn from
the device. By using this circuit, and then the circuit of
Figure 5, +15V can be converted (via +7.5V and –7.5V) to a
nominal – 15V, though with rather high series resistance
(~250Ω).
V
+
R
L1
50
µF
+
1
2
8
7
1 MΩ
V
=
OUT
+
–
V –V
2
R
L2
50
µF
+
–
100 kΩ
3
4
TC7660
6
5
50
µF
+
–
V
–
Figure 11. Splitting a Supply in Half
© 2001 Microchip Technology Inc.
DS21465A
9
TC7660-7 9/30/96
MICROCHIP [ MICROCHIP TECHNOLOGY ]
