MIC22600 Datasheet, PDF (16/17 Pages) Micrel Semiconductor – 1MHz 6A Integrated Switch 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
@6AÈ
3
3.5
4
4.5
5
1
1.47 1.50 1.52 1.54 1.56
1.2
1.45 1.47 1.49 1.51 1.54
1.8
1.46 1.45 1.45 1.47 1.48
2.5
1.61 1.53 1.49 1.47 1.47
3.3
– 1.70 1.62 1.56 1.53
Table 1. Power Dissipation (W) for 6A output
• T_AMB is the Operating Ambient temperature.
MIC22600
Example:
The Evaluation board has 2 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.
September 2007
16
M9999-092007-A