Datasheet

 2001-2012 Microchip Technology Inc. DS21516D-page 9
TC1240/TC1240A
5.4 Input Supply Bypassing
The V
IN
input should be capacitively bypassed to
reduce AC impedance and minimize noise effects due
to the switching internal to the device. The
recommended capacitor should be a large value (at
least equal to C
1
) connected from the input to GND.
5.5 Shutdown Input
The TC1240 and TC1240A are disabled when SHDN is
high, and enabled when SHDN is low. This input cannot
be allowed to float.
FIGURE 5-3: Test Circuit.
5.6 Voltage Doubler
The most common application for charge pump
devices is the doubler (Figure 5-3). This application
uses two external capacitors – C
1
and C
2
(plus a power
supply bypass capacitor, if necessary). The output is
equal to 2 x V
IN
minus any voltage drops due to
loading. Refer to Table 5-1 and Table 5-2 for capacitor
selection.
3
1
2
4
5
C
3
C
1
C
2
V
IN
V
OUT
R
L
TC1240
TC1240A
C-
V
IN
OUT
C+
GND
SHDN
6
+
+
+
Device C
1
C
2
C
3
TC1240
TC1240A
3.3 µF 3.3 µF 3.3 µF