Datasheet

LM2990
www.ti.com SNVS093D –JUNE 1999–REVISED APRIL 2013
Typical Performance Characteristics (continued)
Maximum Power Maximum Power Dissipation
Dissipation (TO-220) (TO-263)
(1)
Figure 23. Figure 24.
(1) The maximum power dissipation is a function of T
Jmax
, θ
JA
, and T
A
. The maximum allowable power dissipation at any ambient
temperature is P
D
= (T
Jmax
− T
A
)/θ
JA
. If this dissipation is exceeded, the die temperature will rise above 125°C, and the LM2990 will
eventually go into thermal shutdown at a T
J
of approximately 160°C. For the LM2990, the junction-to-ambient thermal resistance, is
53°C/W, 73°C/W for the DDPAK/TO-263, and the junction-to-case thermal resistance is 3°C. If the DD[AK/TO-263 package is used, the
thermal resistance can be reduced by increasing the P.C. board copper area thermally connected to the package. Using 0.5 square
inches of copper area, θ
JA
is 50°C/W; with 1 square inch of copper area, θ
JA
is 37°C/W; and with 1.6 or more square inches of copper
area, θ
JA
is 32°C/W.
Typical Applications
Figure 25. Post Regulator for an Isolated Switching Power Supply
The LM2940 is a positive 1A low dropout regulator; refer to its datasheet for further information.
Figure 26. Fixed Current Sink Figure 27. Adjustable Current Sink
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