Micrel, Inc. MIC5264
May 2006
10
M9999-052406
(408) 955-1690
MIC5264 Junction-To-Ambient Thermal Resistance
Package
θ
JA
Recommended
Minimum Footprint
θ
JC
2.5mm x 2.5mm
MLF-10
75°C/W 2°C/W
Thermal Resistance
Substituting P
D
for P
D(max)
and solving for the ambient
operating temperature will give the maximum operating
conditions for the regulator circuit. The junction-to-
ambient thermal resistance for the minimum footprint is
63°C/W. The maximum power dissipation must not be
exceeded for proper operation.
For example, when operating the MIC5264PMYML at an
input voltage of 5.0V at 150mA on V
OUT1
and 100mA on
V
OUT2
with a minimum footprint layout, the maximum
ambient operating temperature T
A
can be determined as
follows:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
°
−°
=
C
TC
W
A
63
125
52.0
T
A
= 92.24°C
Therefore, a 3.0V application at 150mA on Ch1 and 2.8V
at 100mA on Ch2 can accept an ambient operating
temperature of 92°C in a 10-pin 2.5mm x 2.5mm MLF
®
package. For a full discussion of heat sinking and
thermal effects on voltage regulators, refer to the
“Regulator Thermals” section of
Micrel’s Designing with
Low-Dropout Voltage Regulators
handbook. This
information can be found on Micrel's website at:
http://www.micrel.com/_PDF/other/LDOBk_ds.pdf
