TC7660CPA Microchip Technology Inc., TC7660CPA Datasheet - Page 7

• Manufacturer Part Number: TC7660CPA
• Description: DC-DC CONVERTER
• Manufacturer: Microchip Technology Inc.

Specifications of TC7660CPA

• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

5.0
5.1
Figure 5-1 shows typical connections to provide a
negative supply where a positive supply is available. A
similar scheme may be employed for supply voltages
anywhere in the operating range of +1.5V to +10V,
keeping in mind that pin 6 (LV) is tied to the supply
negative (GND) only for supply voltages below 3.5V.
FIGURE 5-1:
The output characteristics of the circuit in Figure 5-1
are those of a nearly ideal voltage source in series with
a 70
a supply voltage of +5V, the output voltage would be
-4.3V.
FIGURE 5-2:
FIGURE 5-3:
10 µF
2002 Microchip Technology Inc.
* V
C
OUT
1
resistor. Thus, for a load current of -10 mA and
APPLICATIONS INFORMATION
Simple Negative Voltage
Converter
+
= -V
+
10 µF
1
2
3
4
for 1.5V
* V
C
1
OUT
TC7660
+
+
Simple Negative Converter.
Paralleling Devices Lowers Output Impedance.
Increased Output Voltage By Cascading Devices.
= -n V
V+
1
2
3
4
1
2
3
4
8
7
6
5
10V
TC7660
+
TC7660
V
for 1.5V
+
“1”
“1”
8
7
6
5
8
7
6
5
V+
V
+
V
+
+
C
10 µF
10V
2
V
OUT
*
10 µF
+
C
1
10 µF
+
+
5.2
To reduce the value of R
converters can be connected in parallel (Figure 5-2).
The output resistance will be reduced by approximately
a factor of n, where n is the number of devices
connected in parallel.
EQUATION
While each device requires its own pump capacitor
(C
(C
should be scaled according to the number of devices
connected in parallel.
5.3
A larger negative multiplication of the initial supply volt-
age can be obtained by cascading multiple TC7660
devices. The output voltage and the output resistance
will both increase by approximately a factor of n, where
n is the number of devices cascaded.
EQUATION
1
2
1
2
3
4
), all devices may share one reservoir capacitor
). To preserve ripple performance, the value of C
1
2
3
4
TC7660
TC7660
“n”
Paralleling Devices
Cascading Devices
“n”
R
R
O UT
O UT
8
7
6
5
8
7
6
5
V
=
O UT
=
n
---------------------------------------------------
n number of devices
R
=
O UT
R
OUT
OUT
n – V
, multiple TC7660 voltage
+
+
of TC7660
10 µF
+
of TC7660
C
R
2
TC7660
V
L
OUT
DS21465B-page 7
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2