TC660 TELCOM [TelCom Semiconductor, Inc], TC660 Datasheet - Page 8

• Manufacturer Part Number: TC660
• Description: 100mA CHARGE PUMP DC-TO-DC VOLTAGE CONVERTER
• Manufacturer: TELCOM [TelCom Semiconductor, Inc]

TC660
a voltage doubler.
brought to within a diode drop of V
reversal) through D. The optional 200
limit the brief latchup current.
charged to 2 V
further part. For V
startup.
Combined Negative Voltage Conversion
and Positive Supply Multiplication
and 8 to provide negative voltage conversion and positive
voltage multiplication simultaneously. In this instance, ca-
pacitors C
tions, respectively, for the generation of the negative volt-
age, while capacitors C
respectively, for the multiplied positive voltage. There is a
penalty in this configuration in that the source impedances
of the generated supplies will be somewhat higher due to
the finite impedance of the common charge pump driver at
pin 2 of the device.
4-12
C 1
Figure 9 shows an improved way of using the TC660 as
In this circuit, C1 is first charged to V
On the next half-cycle, V
Figure 10 combines the functions shown in Figures 3
R = 0.1 – 1M
1
2
3
4
1
and C
1
2
3
4
TC660
Figure 9. Improved Voltage Doubler
Figure 8. Positive Voltage Doubler
IN
200
. D is now reverse-biased and plays no
3
IN
TC660
perform the pump and reservoir func-
< 3V, R may be necessary to ensure
2
8
7
6
5
and C
IN
8
7
6
5
is in series with C1; C2 is then
D 1
4
+
V +
are pump and reservoir,
IN
C 1
(to prevent substrate
D 2
D
R
IN
resistor is only to
and C2 is quickly
+
V OUT =
(2 V + ) – (2 V F )
C 2
C 2
= 2 V IN
V OUT
V IN
Efficient Positive Voltage
Multiplication/Conversion
eration are bidirectional, the charge transfer can be per-
formed backward as easily as forward. Figure 11 shows a
TC660 transforming –5V to +5V. The only problem here is
that the internal clock and switch-drive section will not
operate until some positive voltage has been generated. A
diode and resistor shown dotted in Figure 11 can be used to
"force" the internal regulator on.
150 F
Figure 10. Combined Negative Converter and Positive Multiplier
+
C 1
Since the switches that allow the charge pumping op-
C 1
100mA CHARGE PUMP DC-TO-DC
+
1
2
3
4
Figure 11. Positive Voltage Multiplier
TC660
1
2
3
4
C 2
TC660
+
TELCOM SEMICONDUCTOR, INC.
VOLTAGE CONVERTER
8
7
6
5
8
7
6
5
V +
V OUT = –V –
1 M
V – INPUT
D 1
D 2
V OUT =
(2 V + ) – (2 V F )
+
+
V OUT = –V +
+
C 3
C 4
150 F