TCM828ECT datasheet(15/26 Pages) MICROCHIP

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DS21488B-page 15

TCM828/TCM829

5.0.7

PARALLELING DEVICES

To reduce the value of ROUT, multiple TCM828/

TCM829 devices can be connected in parallel

(Figure 5-5). The output resistance will be reduced by

a factor of N, where N is the number of TCM828/

TCM829 device. Each device will require it’s own pump

capacitor (C1), but all devices may share one reservoir

capacitor

(C2).

However,

preserve

ripple

performance, the value of C2 should be scaled

according to the number of paralleled TCM828/

TCM829 devices.

FIGURE 5-5:

Paralleling TCM828 or

TCM829 Devices to Reduce Output Resistance.

5.0.8

VOLTAGE DOUBLER/INVERTER

Another common application of the TCM828/TCM829

devices is shown in Figure 5-6. 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, while C2 and C4 are

the reservoir capacitors. Because both sub-circuits rely

on the same switches, if either output is loaded, both

will drop toward GND. Make sure that the total current

drawn from both the outputs does not total more than

40 mA.

FIGURE 5-6:

Combined Doubler and

Inverter.

5.0.9

DIODE PROTECTION FOR HEAVY

LOADS

When heavy loads require the OUT pin to sink large

currents, being delivered by a positive source, diode

protection may be needed. The OUT pin should not be

allowed

pulled

above

ground.

This

accomplished

connecting

Schottky

diode

(1N5817) as shown in Figure 5-7.

FIGURE 5-7:

High V– Load Current.

5.0.10

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

VOUT

VOUT =V

"1"

"n"

. . .

TCM828/

TCM829

TCM828/

TCM829

ROUT =

VOUT OF SINGLE DEVICE

NUMBER OF DEVICES

D1, D2 = 1N4148

V+IN

VOUT =V

VOUT =(2VIN)-

TCM828/

TCM829

(VFD1)- (VFD2)

GND

OUT

TCM828/

TCM829

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