LM2941 Datasheet, PDF (10/26 Pages) National Semiconductor (TI) – 1A Low Dropout Adjustable Regulator

LM2941, LM2941C
SNVS770G – JUNE 1999 – REVISED APRIL 2013
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For the LM2941S in the KTT TO-263 package, the junction-to-case thermal rating, θ_JC, is 1°C/W, where the
CASE is defined as the bottom of the package at the center of the TAB area. The junction-to-ambient thermal
performance for the LM2941S in the TO-263 package, using the JEDEC JESD51 standards is summarized in the
following table:
Board
Type
JEDEC
2-Layer
JESD 51-3
JEDEC
4-Layer
JESD 51-7
Thermal
Vias
None
1
2
4
8
θ_JC
1°C/W
1°C/W
1°C/W
1°C/W
1°C/W
θ_JA
73°C/W
35°C/W
30°C/W
26°C/W
24°C/W
6
JA= ^35°C/W
5
JA= ^30°C/W
4
JA= ^26°C/W
JA= ^24°C/W
3
2
1
0 ^{LM2941S (TO-263)}
0
20
40
60
80 100
AMBIENT TEMPERATURE (°C)
Figure 21. P_D(MAX) vs T_A for LM2941S (TO-263)
WSON Mounting
The NGN (Pullback) 8-Lead WSON package requires specific mounting techniques which are detailed in
Application Note 1187 (literature number SNOA401). Referring to the section PCB Design Recommendations
in AN-1187 (Page 5), it should be noted that the pad style which should be used with the WSON package is the
NSMD (non-solder mask defined) type.
The thermal dissipation of the WSON package is directly related to the printed circuit board construction and the
amount of additional copper area connected to the DAP.
The DAP (exposed pad) on the bottom of the WSON package is connected to the die substrate via a conductive
die attach adhesive, and to device pin 2 and pin 7. As such, it is strongly recommend that the DAP area be
connected copper area directly under the DAP that is extended into the ground plane via multiple thermal vias.
Alternately, but not recommended, the DAP area may be left floating (i.e. no direct electrical connection). The
DAP area must not be connected to any potential other than ground.
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