Datasheet

LM1086
SNVS039H –JUNE 2000–REVISED MAY 2013 www.ti.com
The required heat sink is determined by calculating its required thermal resistance (θ
HA(max)
).
θ
HA(max)
= θ
JA(max)
− (θ
JC
+ θ
CH
)
θ
HA (max)
should be calculated twice as follows:
θ
HA (max)
= θ
JA
(max, CONTROL SECTION) - (θ
JC
(CONTROL SECTION) + θ
CH
)
θ
HA (max)
= θ
JA
(max, OUTPUT SECTION) - (θ
JC
(OUTPUT SECTION) + θ
CH
)
If thermal compound is used, θ
CH
can be estimated at 0.2 C/W. If the case is soldered to the heat sink, then a
θ
CH
can be estimated as 0 C/W.
After, θ
HA (max)
is calculated for each section, choose the lower of the two θ
HA (max)
values to determine the
appropriate heat sink.
If PC board copper is going to be used as a heat sink, then Figure 24 can be used to determine the appropriate
area (size) of copper foil required.
Figure 24. Heat sink thermal Resistance vs. Area
Typical Applications
Figure 25. 5V to 3.3V, 1.5A Regulator Figure 26. Adjustable @ 5V
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