TCM828ECT713 Datasheet, PDF (5/9 Pages) Microchip Technology – Switched Capacitor Voltage Converters

Switched Capacitor
Voltage Converters
TCM828
TCM829
R_OUT =
R
OUT
OF
SINGLE DEVICE
NUMBER OF DEVICES
V_I⁺_N
...
2
2
3
3
C1
4
TCM828
C1
4 _TCM828
TCM829
TCM829
5
"1"
1
5
"n"
...
1
V_OUT
...
V_OUT = V_I^–_N
C2
Figure 5. Paralleling TCM828s or TCM829s to Reduce Output Resistance
Voltage Doubler/Inverter
Another common application of the TCM828/829 is
shown in Figure 6. This circuit performs two functions in
combination. C1 and C2 form the standard inverter circuit
described above. C3 and C4 plus the two diodes form the
voltage doubler circuit. C1 and C3 are the pump capacitors
and C2 and C4 are the reservoir capacitors. Because both
sub-circuits rely on the same switches if either output is
loaded, both will droop toward GND. Make sure that the total
current drawn from both the outputs does not total more
than 40mA.
Diode Protection for Heavy Loads
When heavy loads require the OUT pin to sink large
currents being delivered by a positive source, diode protec-
tion may be needed. The OUT pin should not be allowed to
be pulled above ground. This is accomplished by connect-
ing a Schottky diode (1N5817) as shown in Figure 7.
4
GND
TCM828
TCM829
OUT ¹
Figure 7. High V^– Load Current
Layout Considerations
As with any switching power supply circuit good layout
practice is recommended. Mount components as close
together as possible to minimize stray inductance and
capacitance. Also use a large ground plane to minimize
noise leakage into other circuitry.
V+_IN
D1, D2 = 1N4148
3
2
C1
4 _TCM828
D1
TCM829
5
1
V_OUT = V_I^–_N
C2
D2
V_OUT = (2V_IN) –
C3
(V_FD1) – (V_FD2)
C4
Figure 6. Combined Doubler and Inverter
© 2001 Microchip Technology Inc. DS21488A
5
TCM828/829-4 5/22/00