TC1221 Datasheet, PDF (7/16 Pages) Microchip Technology – High Frequency Switched Capacitor Voltage Converters with Shutdown in SOT Packages

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 V_IN) but will droop
at least by R_OUT of the first device multiplied by the I_Q
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 R_OUT, 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
C1
+
V_IN
3
TC1221
4 _TC1222
6
"1"
5 _SHDN
...
V_IN
2
C1
1
3
TC1221
4 _TC1222
+
6
"n"
. . . ⁵ _SHDN
C2
+
V_OUT = -nV_IN
2
1
V_OUT
C2
+
FIGURE 4-5:
PARALLELING MULTIPLE DEVICES TO REDUCE OUTPUT RESISTANCE
R_OUT = R_OUT OF SINGLE DEVICE
NUMBER OF DEVICES
V_IN
...
V_IN
C1
+
Shutdown
Control
3
TC1221
4 _TC1222
6
"1"
5 _SHDN
2
2
3
C1
+
TC1221
4 _TC1222
1
6
"n"
5 _SHDN
1
V_OUT
...
V_OUT = -V_IN
C2
+
 2002 Microchip Technology Inc.
DS21367B-page 7