TC1240A Datasheet, PDF (9/16 Pages) Microchip Technology – Positive Doubling Charge Pumps with Shutdown in a SOT-23 Package

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 C₁) 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.
C₃ ⁺
V_IN
5 _OUT
C+ ⁶
TC1240
+
1
TC1240A
V_IN
C₁
3
4
C-
SHDN
GND ²
+
C₂
R_L
V_OUT
TC1240/TC1240A
5.6 Voltage Doubler
The most common application for charge pump
devices is the doubler (Figure 5-3). This application
uses two external capacitors – C₁ and C₂ (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.
Device
TC1240
TC1240A
C₁
3.3 µF
C₂
3.3 µF
FIGURE 5-3:
Test Circuit.
C₃
3.3 µF
 2003 Microchip Technology Inc.
DS21516C-page 9