TC682
4.3
Paralleling Devices
4.4
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
1
and C
2
, but all can share a single reservoir capacitor.
-5V Regulated Supply From A
Single 3V Battery
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 150Ω source resistance for the converter,
with I
L–
= 10 mA, the charge pump will droop 1.5V.
V
IN
+
10
μF
–
C
1
+
C
1
–
V
IN
10
μF
+
–
C
1
+
C
1
–
V
IN
TC682
+
10
μF
–
C
2
+
V–
OUT
C
2
–
GND
+
10
μF
–
C
2
+
C
2
–
TC682
V–
OUT
GND
Negative
Supply
–
+
C–
OUT
22
μF
GND
FIGURE 4-2:
Paralleling TC682 for Lower Output Source Resistance
+
10
μF
–
+
–
3V
+
10
μF
–
C
1
+
C
1
–
V
IN
Ground
C
2
+
C
2
–
GND
TC682
V
SS
V–
OUT
–
22
μF
+ C
–
OUT
+
–
V
OUT
1
μF
-5 Supply
V
IN
Negative LDO
Regulator
TC54VC2702Exx
V
IN
V
SS
V
OUT
LOW BATTERY
FIGURE 4-3:
Negative Supply Derived from 3V Battery
DS21453C-page 6
©
2006 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
