MIC5238 Micrel Semiconductor, MIC5238 Datasheet - Page 9

• Manufacturer Part Number: MIC5238
• Description: Ultra-Low Quiescent Current/ 150mA Cap LDO Regulator
• Manufacturer: Micrel Semiconductor

current of 150mA. The input ground current under these
conditions is 2mA, while the bias current is only 20 A. If we
calculate the conversion efficiency using the single supply
approach, it is as follows:
Input power = V
current + V
Input power = 2.5V
380.5mW
Output power = 1V
Efficiency = 150/380.5
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:
August 2003
MIC5238
IN
ground current)
IN
output current + V
0.15 = 150mW
150mA + 2.5
100 = 39.4%
IN
(0.0002+0.002) =
(V
BIAS
ground
9
Input power = V
+ V
Input power = 1.5
225mW
Output power = 1V
Efficiency = 150/225
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.
BIAS
x V
BIAS
IN
ground current
output current + V
150mA + 1.5
150mA = 150mW
100 = 66.6 %
0.002 + 2.5
IN
V
IN
ground current
MIC5238
0.0002 =
Micrel