tc7660h Microchip Technology Inc., tc7660h Datasheet - Page 5

• Manufacturer Part Number: tc7660h
• Description: High Frequency 7660 Dc-to-dc Voltage Converte
• Manufacturer: Microchip Technology Inc.

HIGH FREQUENCY 7660 DC-TO-DC
VOLTAGE CONVERTER
Positive Voltage Multiplication
voltage multiplication using the circuit shown in Figure 7. In
this application, the pump inverter switches of the TC7660H
are used to charge C
is the supply voltage and V
diode D
supply voltage (V
C
or twice the supply voltage minus the combined forward
voltage drops of diodes D
on the output current, but for V
of 10mA, it will be approximately 60 .
© 2001 Microchip Technology Inc.
2
1.0 F
. The voltage thus created on C
The TC7660H may be employed to achieve positive
The source impedance of the output (V
1
). On the transfer cycle, the voltage on C
C 1
+
1
2
3
4
Figure 7. Positive Voltage Multiplier
TC7660H
1
2
3
4
+
Figure 6. External Clocking
) is applied through diode D
TC7660H
1
2
3
4
1
to a voltage level of V
DS21466A
TC7660H
8
7
6
5
1
"1"
F
and D
is the forward voltage drop of
8
7
6
5
+
D 1
= 5V and an output current
+
2
V +
2
V +
8
7
6
5
becomes (2 V
.
1 k
Figure 5. Paralleling Devices Lowers Output Impedance
C 1
D 2
V
+
+
OUT
+
+
– V
V OUT =
(2 V + ) – (2 V F )
2
) will depend
C 2
1.0 F
to capacitor
F
V +
+
(where V
1
) – (2 V
CMOS
GATE
V OUT
plus the
C 1
F
),
+
5
Combined Negative Voltage Conversion
and Positive Supply Multiplication
8 to provide negative voltage conversion and positive volt-
age multiplication simultaneously. This approach would be,
for example, suitable for generating +9V and –5V from an
existing +5V supply. In this instance, capacitors C
perform the pump and reservoir functions, respectively, for
the generation of the negative voltage, while capacitors C
and C
plied positive voltage. There is a penalty in this configuration
which combines both functions, however, 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.
Figure 8. Combined Negative Converter and Positive Multiplier
1
2
3
4
+
C 1
Figure 8 combines the functions shown in Figures 3 and
TC7660H
4
are pump and reservoir, respectively, for the multi-
"n"
1
2
3
4
TC7660H
8
7
6
5
C 2
+
8
7
6
5
V +
+
C 2
R L
D 1
D 2
V OUT =
(2 V + ) – (2 V F )
TC7660H
+
+
R L
TC7660H-2 10/1/96
V OUT =
– (V + – V F )
C 3
C 4
1
and C
3
2