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4.5 Control Loop Gain and Phase Measurement Procedure
7. The control loop gain can be measured by
20 LOG
ǒ
ChannelB
ChannelA
Ǔ
4.6 Equipment Shutdown
5 TPS40192EVM Typical Performance Data and Characteristic Curves
5.1 Efficiency
h -Efficiency-%
50
55
60
65
70
75
80
85
90
95
I -LoadCurrent- A
O
0 2 4 6 8 10 12
100
V =8V
I
V =12V
I
V =14V
I
TPS40192EVM Typical Performance Data and Characteristic Curves
1. Connect a 1-kHz to 1-MHz isolation transformer to TP12 and TP13 as shown in Figure 3 .
2. Connect the input signal amplitude measurement probe (channel A) to TP12 as shown in Figure 3 .
3. Connect the output signal amplitude measurement probe (channel B) to TP13 as shown in Figure 3 .
4. Connect the ground lead of channel A and channel B to TP11 and TP14 as shown in Figure 3 .
5. Inject a 30-mV or less signal across R14 through the isolation transformer.
6. Sweep the frequency from 1 kHz to 1 MHz with a 10-Hz or lower post filter
8. The control loop phase is measured by the phase difference between channel A and channel B.
9. The control-to-output response (power stage transfer function) can be measured by connecting the
channel A probe to TP6 (COMP) and the channel B probe to TP13.
10. The output-to-control response (error amplifier transfer function) can be measured by connecting the
channel B probe to TP6 (COMP) and the channel A probe to TP12.
11. Disconnect the isolation transformer from TP12 and TP13 before making other measurements. (The
signal injection into feedback may interfere with the accuracy of other measurements.)
1. Shut down the oscilloscope.
2. Shut down LOAD1.
3. Shut down V
IN
.
4. Shut down the fan.
Figure 4 through Figure 8 present typical performance curves for the TPS40192EVM-001. Because actual
performance data can be affected by measurement techniques and environmental variables, these curves
are presented for reference only and may differ from actual field measurements.
Figure 4. TPS40192EVM-001 Efficiency vs Load Current,
Vin = 8 V - 14 V, Vout = 1.8 V, Iout = 0 A - 10 A
SLVU194 – January 2007 Using the TPS40192EVM-001, A 12-V Input, 1.8-V Output, 10-A Synchronous Buck Converter 11
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