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3.5 Start Up / Shut Down Procedure
3.6 Control Loop Gain and Phase Measurement Procedure
7. Control-loop gain can be measured by
20 LOG
ǒ
ChannelB
ChannelA
Ǔ
3.7 Equipment Shutdown
4 TPS40077EVM Typical Performance Data and Characteristic Curves
4.1 Efficiency
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 8 9 10
I -LoadCurrent- A
O
h -Efficiency-%
V =8.0V
IN
V =16.0V
IN
V =12.0V
IN
TPS40077EVM Typical Performance Data and Characteristic Curves
1. Increase V
12V_IN
from 0 V to 12 V DC.
2. Vary LOAD1 from 0–10 A DC
3. Vary V
12V_IN
from 8 V DC to 16 V DC
4. Decrease LOAD1 to 0 A.
1. Connect 1 kHz–1 MHz isolation transformer to TP3 and TP6 as shown in Figure 4
2. Connect input-signal amplitude-measurement probe (channel A) to TP3 as shown in Figure 4
3. Connect output-signal amplitude measurement probe (channel B) to TP6 as shown in Figure 4
4. Connect ground lead of channel A and channel B to TP8 as shown in Figure 4
5. Inject 25 mV or less signal across TP3 and TP6 through an isolation transformer
6. Sweep frequency from 1 kHz to 1 MHz with 10 Hz or lower post filter
8. Control-loop phase is measured by the phase difference between channel A and channel B
9. Disconnect isolation transformer from TP3 and TP6 before making other measurements (Signal
injection into feedback may interfere with accuracy of other measurements)
1. Shut Down Oscilloscope
2. Shut down LOAD1
3. Shut down V
12V_IN
Figure 5 through Figure 10 present typical performance curves for the TPS40077EVM-001. Since actual
performance data can be affected by measurement techniques and environmental variables, these curves
are presented for reference and may differ from actual field measurements.
Figure 5. TPS40077EVM-001 Efficiency
8 Using the TPS40077EVM-001 12-V Input, 1.8-V Output, SLVU192A – February 2007 – Revised March 2008
10-A Synchronous Buck Converter
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