TC1121 datasheet(6/14 Pages) MICROCHIP

6 / 14 page

TC1121

DS21358C-page 6

3.4

Cascading Devices

To produce greater negative magnitudes of the initial

supply voltage, the TC1121 may be cascaded (see

Figure 3-2). Resulting output resistance is approxi-

mately equal to the sum of individual TC1121 ROUT

values. The output voltage (where n is an integer

representing the number of devices cascaded) is

defined by VOUT = -n (VIN).

3.5

Paralleling Devices

To reduce output resistance, multiple TC1121s may be

paralleled (see Figure 3-3). Each device needs a pump

capacitor C1, but the reservoir capacitor C2 serves all

devices. The value of C2 should be increased by a

factor of n (the number of devices).

FIGURE 3-2:

Cascading TC1121s to Increase Output Voltage

FIGURE 3-3:

Paralleling TC1121s to Reduce Output Resistance

C1n

VIN

C2n

TC1121

GND

OSC

CAP+

CAP–

SHDN

VOUT

VIN

VOUT

VIN

SHDN

SHDN*

“1”

“n”

*SHDN should be tied to VIN if not used.

C1n

V+IN

TC1121

GND

OSC

CAP+

CAP–

SHDN

VOUT

VIN

SHDN

SHDN*

*SHDN should be tied to VIN if not used.

“1”

“n”

OSC

ROUT = ROUT (of TC1121)/n(number of devices)

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