MIC22700 Datasheet, PDF (16/21 Pages) Micrel Semiconductor – 1MHz, 7A Integrated Switch High Efficiency Synchronous Buck Regulator

Micrel, Inc.
• Rθ_JA is a combination of junction to case thermal
resistance (Rθ_JC) and Case-to-Ambient thermal
resistance (Rθ_CA), since thermal resistance of
the solder connection from the ePAD to the PCB
is negligible; Rθ_CA is the thermal resistance of
the ground plane to ambient, so Rθ_JA = Rθ_JC +
Rθ_CA.
VINÆ
VOUT
@7AÈ
0.7V
1.2V
1.8V
2.5V
3.3V
2.6V
2.073
2.133
2.207
—
—
3.3V
1.884
1.896
1.934
1.953
—
3.6V
1.836
1.853
1.873
1.881
1.423
4.5V
1.784
1.786
1.814
1.797
1.79
5.5V
1.791
1.796
1.826
1.803
1.789
Table 1. Power Dissipation (W) for 7A output
• T_AMB is the Operating Ambient temperature.
MIC22700
Example:
The Evaluation board has two copper planes
contributing to an Rθ_JA of approximately 25°C/W. The
worst case Rθ_JC of the MLF 4x4 is 14^oC/W.
Rθ_JA = Rθ_JC + Rθ_CA
Rθ_JA = 14 + 25 = 39^oC/W
To calculate the junction temperature for a 50°C
ambient:
T_J = T_AMB+P_DISS . Rθ_JA
T_J = 50 + (1.5 x 39)
T_J = 109°C
This is below the maximum of 125°C.
July 2009
16
M9999-072209-B