TC1121 Datasheet, PDF (6/14 Pages) Microchip Technology – 100mA Charge Pump Voltage Converter with Shutdown

TC1121
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 R_OUT
values. The output voltage (where n is an integer
representing the number of devices cascaded) is
defined by V_OUT = -n (V_IN).
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
N
C
N
C
V_IN ⁸
AP
SC
AP
SC ⁷
C1121
C1121
1
ND
1n
ND
HDN
HDN*
HDN
HDN*
AP
UT
1"
AP
UT
n"
UT
2n
2
SHDN should be tied to V_IN if ot used.
FIGURE 3-3:
PARALLELING TC1121s TO REDUCE OUTPUT RESISTANCE
N
FC
N
2 _CAP+
SC
SC
C1121
1n
C1
ND
HDN
HDN*
AP
UT
1"
C
AP
SC
C1121
ND
HDN
AP
UT
n"
HDN*
2
UT ^{= R} UT ^{of TC1121)/n(number of devices)}
IN ^{if not used.}
DS21358B-page 6
 2002 Microchip Technology Inc.