TC7660SVOA723 データシートの表示（PDF） - Microchip Technology
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TC7660SVOA723 Datasheet PDF : 24 Pages
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TC7660S
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 +12V,
keeping in mind that pin 6 (LV) is tied to the supply
negative (GND) only for supply voltages below 3.5V.
The dynamic output impedance of the TC7660S is due,
primarily, to capacitive reactance of the charge transfer
capacitor (C1). Since this capacitor is connected to the
output for only half of the cycle, the equation is:
EQUATION
where:
XC = -2---f-2-C----1- = 3.18
f = 10 kHz and C1 = 10 µF.
C1 +
10 µF
V+
1
8
2
7
3 TC7660S 6
4
5
VOUT*
C2
+ 10 µF
5.2 Paralleling Devices
Any number of TC7660S voltage converters may be
paralleled to reduce output resistance (Figure 5-2). The
reservoir capacitor, C2, serves all devices, while each
device requires its own pump capacitor, C1. The resul-
tant output resistance would be approximately:
* VOUT = -V+ for 1.5V V+ 12V
FIGURE 5-1:
Simple Negative Converter.
EQUATION
ROUT = n---R----On---uU---m-T---b---eo---rf----To---fC---d-7--e-6--v-6-i--0c---eS--s---
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.
V+
1
8
+
C1
2
7
3 TC7660S 6
4 “1” 5
+
C1
1
8
2
7
3 TC7660S 6
RL
4 “n” 5
+ C2
FIGURE 5-2:
Paralleling Devices Lowers Output Impedance.
+
10 µF
V+
1
8
2
7
3 TC7660S 6
4 “1” 5
+
10 µF
1
8
2
7
3 TC7660S 6
4 “n” 5
* VOUT = -n V+ for 1.5V V+ 12V
+ 10 µF
FIGURE 5-3:
Increased Output Voltage By Cascading Devices.
VOUT *
+ 10 µF
2001-2015 Microchip Technology Inc.
DS20001467C-page 9
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