MIC38300 Datasheet, PDF (8/10 Pages) Micrel Semiconductor – 3A SuperLNR™ Low Noise High Efficiency Regulator

Micrel, Inc.
case, inductor selection becomes increasingly critical in
efficiency calculations. As the inductors are reduced in
size, the DC resistance (DCR) can become quite
significant. The DCR losses can be calculated as
follows:
L_P_D = I_OUT2 × DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as follows;
MIC38300
Efficiency
_
Loss
=
⎡
⎢^{1 −}
⎢⎣
⎜⎜⎝⎛
V_OUT ×
V_OUT × I_OUT
I_OUT
+L_
P_D
⎟⎟⎠⎞⎥⎥⎦⎤
× 100
Efficiency loss due to DCR is minimal at light loads and
gains significance as the load is increased. Inductor
selection becomes a trade-off between efficiency and
size in this case.
July 2007
8
M9999-070607
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