Micrel, Inc. MIC5305
June 2007 10
M9999-062507
Table 1 shows junction-to-ambient thermal resistance for
the MIC5305 in the 6-pin 2mm × 2mm MLF
®
package.
Package
θJA Recommended
Minimum Footprint
θJC
6-Pin 2x2 MLF
®
93°C/W 2°C/W
Table 1. 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
(the minimum amount of copper that you can solder the
part to) is 93°C/W, from Table 1. The maximum power
dissipation must not be exceeded for proper operation.
For example, when operating the MIC5305-2.9BML at
an input voltage of 5.0V and 150mA load with a
minimum footprint layout, the maximum ambient
operating temperature T
A
can be determined as follows:
C/W93
TC125
0.32W
A
°
−°
=
T
A
= 95.2°C
Therefore, a 2.9V application at 150mA of output current
can accept an ambient operating temperature of 95.2°C
in a 6-pin 2mm x 2mm MLF
®
package. For a full dis-
cussion 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
