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UG-439
Measuring Efficiency of the Buck Regulator
Measure the efficiency, η, by comparing the input power with
the output power.
×
V
I
=
OUT
OUT
η
×
V
I
IN
IN
Measure the input and output voltages as close as possible to the
input and output capacitors to reduce the effect of IR drops.
The buck regulator efficiency plots for V
1.8 V are shown in Figure 11 and Figure 12, respectively.
100
90
80
70
60
50
40
30
20
10
0
1
10
Figure 11. Buck Regulator Efficiency, V
100
PSM
PWM
90
80
70
60
50
40
30
20
10
0
1
10
Figure 12. Buck Regulator Efficiency, V
Measuring Inductor Current
Measure the inductor current by removing one end of the inductor
from its pad and connecting a current loop in series. Connect a
current probe to this wire.
Measuring Line Regulation of LDO Regulators
For line regulation measurements, the output of the regulator
is monitored while its input is varied. For optimal line regula-
tion, the output must change as little as possible with varying
input levels.
= 3.3 V and V
OUT2
OUT2
PSM MODE
PWM MODE
100
1000
10000
I
(mA)
LOAD
= 4.2 V, V
= 3.3 V
IN2
OUT2
100
1k
10k
I
(mA)
LOAD
= 3.6 V, V
= 1.8 V
IN2
OUT2
To ensure that the device is not in dropout mode during this
measurement, V
(or 2.3 V, whichever is greater) and V
a fixed 3.3 V output needs V
5.5 V. This measurement can be repeated under different load
conditions. Figure 13 shows the typical line regulation performance
of the LDO regulator with a fixed 3.3 V output.
3.317
=
3.316
3.315
3.314
3.313
3.312
3.311
3.6
Figure 13. V
Measuring Load Regulation of LDO Regulators
For load regulation measurements, the regulator output is
monitored while the load is varied. For optimal load regulation,
the output must change as little as possible with varying loads.
The input voltage must be held constant during this measurement.
The load current can be varied from 0 mA to 300 mA. Figure 14
shows the typical load regulation performance of the LDO
regulator with a 3.3 V output for different input voltages.
3.3160
3.3155
3.3150
3.3145
3.3140
3.3135
3.3130
3.3125
3.3120
3.3115
3.3110
0
Figure 14. V
Rev. A | Page 6 of 13
Evaluation Board User Guide
must be varied between V
IN
OUT
maximum. For example,
IN
to be varied between 3.8 V and
IN
4.1
4.6
V
(V)
IN
vs. V
, LDO Line Regulation for an Output of 3.3 V
OUT
IN
50
100
150
200
I
(mA)
LOAD
vs. I
, LDO Load Regulation
OUT
LOAD
nominal + 0.5 V
I
= 1mA
LOAD
I
= 10mA
LOAD
I
= 100mA
LOAD
I
= 200mA
LOAD
I
= 300mA
LOAD
5.1
5.6
V
= 3.6V
IN
V
= 4.2V
IN
V
= 5.5V
IN
250
300
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