iru431al International Rectifier Corp., iru431al Datasheet - Page 5

• Manufacturer Part Number: iru431al
• Description: Low -voltage Adjustable Precision Shunt Regulator -
• Manufacturer: International Rectifier Corp.

Thermal Design
The IRU431L is offered in the surface mount SOT-23 (L)
packages. The SOT-23 package has the maximum power
dissipation capability of 150mW at T
rating factor of -1.2mW / C.
The table below summarizes the maximum power dissi-
pation capability of each package versus ambient tem-
perature.
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:
As shown in the power dissipation table, both packages
can handle this power dissipation.
Rev. 1.8
02/20/02
SOT-23
Pkg
P
Where:
P
For our example:
P
MAX
MAX
MAX
= V
= Maximum power dissipation of the 431L
= 3.3
150mW
25
KA
Ambient Temperature (T
o o
o o
6 - 3.3
132mW
V
100
40
MAX
R
- V
B
p p = 89mW
KA
120mW
p p
50
A
=25 C with the de-
108mW
60
A
) -& & C
96mW
70
www.irf.com
Stability
The IRU431L has many different domains of stability as
a function of the cathode current. As is typical of three-
terminal shunt regulators, the IRU431L has many do-
mains of stability. The actual domain in which any prac-
tical circuit operates is related to cathode current. In
general the device will be unconditionally stable for any
cathode current if a capacitor, 1 F or larger, is connected
between the cathode and the anode. If the cathode cur-
rent is always higher than 3mA under minimum line and
maximum load conditions, the capacitor value can be
reduced to 0.01 F and the system will be stable.
IRU431L / IRU431AL
5