Datasheet
TC682
DS21453D-page 6 2002-2012 Microchip Technology Inc.
4.3 Paralleling Devices
Paralleling multiple TC682s reduces the output
resistance of the converter. The effective output
resistance is the output resistance of a single device
divided by the number of devices. As illustrated in
Figure , each requires separate pump capacitors C
1
and C
2
, but all can share a single reservoir capacitor.
4.4 -5V Regulated Supply From A
Single 3V Battery
Figure 4-3 shows a -5V power supply using one 3V
battery. The TC682 provides -6V at V
OUT
, which is
regulated to -5V by the negative LDO. The input to the
TC682 can vary from 3V to 5.5V without affecting
regulation appreciably. A TC54 device is connected to
the battery to detect undervoltage. This unit is set to
detect at 2.7V. With higher input voltage, more current
can be drawn from the outputs of the TC682. With 5V
at V
IN
, 10 mA can be drawn from the regulated output.
Assuming 150 source resistance for the converter,
with I
L
–
= 10 mA, the charge pump will droop 1.5V.
FIGURE 4-2: Paralleling TC682 for Lower Output Source Resistance
FIGURE 4-3: Negative Supply Derived from 3V Battery
10 μF
10 μF
10 μF
10 μF
22 μF
V
IN
GND
GND
Negative
Supply
TC682 TC682
GND
+
–
+
–
+
–
+
–
+
–
V
IN
C
1
+
C
2
+
C
1
–
C
2
–
V
–
OUT
V
IN
C
1
+
C
2
+
C
1
–
C
2
–
V
–
OUT
C
–
OUT
V
SS
V
SS
GND
TC682
3V
Ground
-5 Supply
LOW BATTERY
Negative LDO
Regulator
TC54VC2702Exx
1 μF
+
–
+
–
+
–
+
–
+
–
10
μ
F
22
μ
F
10
μ
F
V
IN
C
1
+
C
2
+
C
1
–
C
2
–
V
IN
V
IN
V
OUT
V
OUT
V
–
OUT
C
OUT
–