TC1121_06 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:
+
C1
V_I⁺_N
FC
V_IN ⁸
2 _CAP+
OSC
TC1121
3 _GND
SHDN
+
C1n
SHDN*
4 _CAP– V_OUT 5
“1”
C2
+
FC
V_IN ⁸
2 _CAP+
OSC ⁷
TC1121
3
GND
SHDN
4 _CAP–
V_OUT ⁵
“n”
SHDN*
V_OUT
C2n
+
*SHDN should be tied to V_IN if not used.
Cascading TC1121s to Increase Output Voltage
+
C1
V+_IN
FC
V_IN ⁸
2 _CAP+
OSC ⁷ OSC
TC1121
3 _GND
SHDN
C1n ⁺
SHDN*
4 _CAP– V_OUT 5
“1”
FC
V_IN ⁸
2 _CAP+
OSC ⁷
TC1121
3
GND
SHDN
4 _CAP–
V_OUT ⁵
“n”
SHDN*
C2
+
R_OUT = R_OUT (of TC1121)/n(number of devices)
*SHDN should be tied to V_IN if not used.
FIGURE 3-3:
Paralleling TC1121s to Reduce Output Resistance
DS21358C-page 6
© 2006 Microchip Technology Inc.