TC7660EOATR 데이터 시트보기 (PDF) - Microchip Technology
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TC7660EOATR Datasheet PDF : 20 Pages
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TC7660
5.0 APPLICATIONS INFORMATION
5.1 Simple Negative Voltage
Converter
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.
5.2 Paralleling Devices
To reduce the value of ROUT, multiple TC7660 voltage
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
ROUT
=
------R----O---U----T------o----f---T----C----7----6---6---0--------
n number of devices
C1 +
10 µF
V+
1
8
2
7
TC7660
3
6
4
5
VOUT*
C2
+ 10 µF
* VOUT = -V+ for 1.5V V+ 10V
FIGURE 5-1:
Simple Negative Converter.
The output characteristics of the circuit in Figure 5-1
are those of a nearly ideal voltage source in series with
a 70resistor. Thus, for a load current of -10 mA and
a supply voltage of +5V, the output voltage would be
-4.3V.
While each device requires its own pump capacitor
(C1), all devices may share one reservoir capacitor
(C2). To preserve ripple performance, the value of C2
should be scaled according to the number of devices
connected in parallel.
5.3 Cascading Devices
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
VOUT = –nV+
ROUT = n ROUT of TC7660
V+
1
8
+
C1
2
7
TC7660
3
6
4 “1” 5
+
C1
1
8
2
7
TC7660
3
6
RL
4 “n” 5
FIGURE 5-2:
Paralleling Devices Lowers Output Impedance.
+
10 µF
V+
1
8
2
7
TC7660
3
6
4 “1” 5
+
10 µF
1
8
2
7
TC7660
3
6
4 “n” 5
* VOUT = -n V+ for 1.5V V+ 10V
+ 10 µF
FIGURE 5-3:
Increased Output Voltage By Cascading Devices.
+ C2
VOUT *
10 µF
+
2002-2011 Microchip Technology Inc.
DS21465C-page 7
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