LM2662, LM2663
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SNVS002D –JANUARY 1999–REVISED MAY 2013
CASCADING DEVICES
Cascading the LM2662s (or LM2663s) is an easy way to produce a greater negative voltage (as shown in
Figure 21). If n is the integer representing the number of devices cascaded, the unloaded output voltage Vout is
(−nVin). The effective output resistance is equal to the weighted sum of each individual device:
(5)
A three-stage cascade circuit shown in Figure 22 generates −3Vin, from Vin.
Cascading is also possible when devices are operating in doubling mode. In Figure 23, two devices are
cascaded to generate 3Vin.
An example of using the circuit in Figure 22 or Figure 23 is generating +15V or −15V from a +5V input.
Note that, the number of n is practically limited since the increasing of n significantly reduces the efficiency and
increases the output resistance and output voltage ripple.
Figure 21. Increasing Output Voltage by Cascading Devices
Figure 22. Generating −3Vin from +Vin
Figure 23. Generating +3Vin from +Vin
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