TC1221 datasheet(7/16 Pages) MICROCHIP

7 / 16 page

 2002 Microchip Technology Inc.

DS21367B-page 7

TC1221/TC1222

4.7

Cascading Devices

Two or more TC1221/TC1222 can be cascaded to

increase output voltage (Figure 4-4). If the output is

lightly loaded, it will be close to (-2 x VIN) but will droop

at least by ROUT of the first device multiplied by the IQ

of the second. It can be seen that the output resistance

rises rapidly for multiple cascaded devices.

4.8

Paralleling Devices

To reduce the value of ROUT, multiple TC1221/

TC1222’s can be connected in parallel (Figure 4-5).

The output resistance will be reduced by a factor of N

where N is the number of TC1221/TC1222. Each

device will require its own pump capacitor (C1), but all

devices may share one reservoir capacitor (C2).

However, to preserve ripple performance the value of

C2 should be scaled according to the number of

paralleled TC1221/TC1222.

FIGURE 4-4:

CASCADING MULTIPLE DEVICES TO INCREASE OUTPUT VOLTAGE

FIGURE 4-5:

PARALLELING MULTIPLE DEVICES TO REDUCE OUTPUT RESISTANCE

VIN

VOUT

VOUT =-nVIN

TC1221

TC1222

TC1221

TC1222

...

SHDN

VIN

"1"

"n"

VOUT

VOUT =-VIN

ROUT = ROUT OF SINGLE DEVICE

VIN

NUMBER OF DEVICES

TC1221

TC1222

TC1221

TC1222

...

SHDN

Shutdown

Control

VIN

"1"

"n"

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