MIC5238(2003) 데이터 시트보기 (PDF) - Micrel

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MIC5238
(Rev.:2003)

Ultra-Low Quiescent Current, 150mA µCap LDO Regulator

Micrel 

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 = VIN × output current + VIN × (VBIAS ground

current + VIN 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:

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Input power = VIN × output current + VIN × VIN ground current

+ VBIAS x VBIAS 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

9

MIC5238

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