CAT660_07 Datasheet, PDF (12/16 Pages) Catalyst Semiconductor – 100mA CMOS Charge Pump Inverter/Doubler

CAT660
CASCADE OPERATION FOR HIGHER NEGATIVE VOLTAGES
The CAT660 can be cascaded as shown in figure 11 to generate more negative voltage levels. The output resistance
is approximately the sum of the individual CAT660 output resistance.
VOUT= -N x VIN, where N represents the number of cascaded devices.
+
C1
+VIN
8
8
2 _CAT660
3
"1"
+
C1
2 _CAT660
3
"N"
4
5
4
5
VOUT = -NVIN
+ ^C2
+ ^C2
Figure 11: Cascading to Increase Output Voltage
PARALLEL OPERATION
Paralleling CAT660 devices will lower output resistance. As shown in figure 12, each device requires its own pump
capacitor, C2, but the output reservoir capacitor is shared with all devices. The value of C2 should be increased by
a factor of N, where N is the number of devices.
The output impedance of the combined CAT660's is:
ROUT(Of "N" CAT660’s)= ^{ROUT (Of the CAT660)}
N (Number of devices)
+
C1
+VIN
8
2 _CAT660
3
"1"
+
C1
4
5
8
2 _CAT660
3
"N"
4
5
Doc. No. MD-5000, Rev. W
C2
+
Figure 12: Paralleling Devices Reduce Output Resistance
12