MIC5238 Datasheet, PDF (9/10 Pages) Micrel Semiconductor – Ultra-Low Quiescent Current, 150mA uCap LDO Regulator

MIC5238
current of 150mA. The input ground current under these
conditions is 2mA, while the bias current is only 20µA. If we
calculate the conversion efficiency using the single supply
approach, it is as follows:
Input power = V_IN × output current + V_IN × (V_BIAS ground
current + V_IN ground current)
Input power = 2.5V × 150mA + 2.5 × (0.0002+0.002) =
380.5mW
Output power = 1V × 0.15 = 150mW
Efficiency = 150/380.5 × 100 = 39.4%
Now, using a lower input supply of 1.5V, and powering the
bias voltage only from the 2.5V input, the efficiency is as
follows:
Micrel
Input power = V_IN × output current + V_IN × V_IN ground current
+ V_BIAS x V_BIAS ground current
Input power = 1.5 × 150mA + 1.5 × 0.002 + 2.5 × 0.0002 =
225mW
Output power = 1V × 150mA = 150mW
Efficiency = 150/225 × 100 = 66.6 %
Therefore, by using the dual supply MIC5238 LDO the
efficiency is nearly doubled over the single supply version.
This is a valuable asset in portable power management
applications equating to longer battery life and less heat
being generated in the application.
This in turn will allow a smaller footprint design and an
extended operating life.
August 2003
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MIC5238