US431L/431AL
In our previous example, the maximum power dissipa-
tion of the device is calculated under no load and maxi-
mum input supply condition.
The maximum power is calculated using the following
equation :
VMAX - VKA
æ
è
ö
PMAX = VKA ´
ç
÷
ø
RB
Where :
PMAX
Maximum power dissipation of the 431L
=
For our example :
6 - 3.3
æ
ö
PMAX = 3.3 ´
= 89 mW
ç
è
÷
ø
100
As shown in the power dissipation table, both packages
can handle this power dissipation.
Stability
The US431L has many different regions of stability do-
main as a function of the cathode current which are typi-
cal characteristics of the 3 terminal shunt regulators.
However in general the device will be unconditionaly
stable for any cathode current if the capacitor, CO =
1 uF or bigger is connected from Cathode to Anode
pins. If the cathode current is always kept higher than
500uA under minimum line and maximum load condi-
tions , the CO can be cut to 0.01uF and the system will
be stable.
Rev. 1.2
5/11/98
2-5
UNISEM [ UNISEM ]
