Datasheet

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4.5 Control Loop Gain and Phase Measurement Procedure
10. Control loop gain can be measured by
20 LOG
ǒ
ChannelB
ChannelA
Ǔ
5 TPS40040EVM Typical Performance Data and Characteristic Curves
0
10
20
30
40
50
60
70
80
90
100
0 2 4 6 8 10 12
I -LoadCurrent- A
LOAD
h
-Efficiency-%
V =4.5V
IN
V =5V
IN
V =5.5V
IN
TPS40040EVM Typical Performance Data and Characteristic Curves
5. Measure output ripple.
6. Decrease LOAD1 to 0 A.
7. Decrease V
IN
to 0 Vdc.
1. Connect 1-kHz to 1-MHz isolation transformer to TP12 and TP13 as show in Figure 4 .
2. Connect input signal amplitude measurement probe (channel A) to TP12 as shown in Figure 4 .
3. Connect output signal amplitude measurement probe (channel B) to TP13 as shown in Figure 4 .
4. Connect ground lead of channel A and channel B to TP11 and TP14 as shown in Figure 4 .
5. Increase V
IN
from 0 V to 5 Vdc.
6. Adjust LOAD1 to desired load between 0 Adc and 10 Adc.
7. Adjust V
IN
to desired load between 4.5 Vdc and 5.5 Vdc.
8. Inject 30-mV or less signal across R14 through isolation transformer.
9. Sweep frequency from 1 kHz to 1 MHz with 10 Hz or lower post filter.
11. Control loop phase is measured by the phase difference between channel A and channel B.
12. Control-to-output response (power stage transfer function) can be measured by connecting channel A
probe to TP6 (COMP) and channel B probe to TP13.
13. Output-to-control response (error amplifier transfer function) can be measured by connecting channel
B probe to TP6 (COMP) and channel A probe to TP12.
14. Disconnect isolation transformer from TP12 and TP13 before making other measurements (signal
injection into feedback may interfere with accuracy of other measurements).
15. Decrease LOAD1 to 0 A.
16. Decrease V
IN
to 0 Vdc.
Figure 5 and Figure 10 present typical performance curves for the TPS40040EVM-001. Because 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. TPS40040EVM-001 Efficiency Curves
SLUU266 – January 2007 Using the TPS40040EVM-001: A 12-V Input, 1.8-V Output, 10-A Synchronous Buck Converter 11
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