User manual

page 65
Analog System Lab Kit PRO
The unregulated input is connected at screw terminal CN5. Output load is connected
to screw terminal at CN6.The switching waveform can be observed at the terminal
TP4.The evaluation module has a switching frequency of 200 kHz. This frequency
is decided by the combination of R201 and C213. The duty cycle of this waveform
varies linearly with the input voltage for a constant output voltage, as shown
below.
What should be the value of the external resistance to be connected between
TP8 and Groundtocongurethe evaluationmodule togenerateregulated
output voltage of 5V?
Simulatetheconguredcircuitusingasimulator.Thetypicalwaveformswill
be of the form shown in Figure 12.2.
In this experiment, we wish to study the line and load regulation for the TPS40200
integratedcircuitwhenitisconguredtogeneratea5VDCoutput.
Conguretheonboardevaluationmoduletogenerateconstant5VDCoutputby
making the changes in the feedback path using the available terminals.
12.2Specications
12.3 Measurements to be taken
12.4 What should you submit?
experiment 12
Figure 12.2: Simulation waveforms - TP3 is the PWM waveform
and TP4 is the switching waveform
The output ripple voltage can be measured across terminals TP5 and TP7 by simply
placing the oscilloscope probes. The oscilloscope must be set for
0.7
1
V
V
VV
RR
R
VVdutycycle
TP
TP
M
R
TP
J
TP
TP
R
C
209207
209
205
207
209
20
201
203
204
201
213
out
ref
ref
out in
8
$
X
=
=
=
=
b
b
+
impedance,
AC coupling. The same terminals can be used for the measurement of the regulated
output DC voltage using a voltmeter.
What should be the value of the external
resistance for the regulated output of 5V?
Obtain the Line Regulation: Vary the input voltage from 10V to 15V in steps
of 0.5V and plot the output voltage as the function of the input voltage for a
constant output load.
Obtain the Load Regulation: Vary the load (within the permissible limits) such
that load current varies and obtain the output voltage for constant input
voltage. Plot the output voltage as a function of the load current.
1
1
3
4
2
2
TP3
TP4
Vin
Vout
1.00
0.00
20.00
-10.00
10.00
10.00
5.01
4.98
10.00m 10.02m 10.05m 10.07m 10.10m
Congure the on board evaluation module to generate a regulated output
voltage of 5V, and observe the waveforms mentioned in Figure 12.2 and
compare with the simulation results.
Vary the input voltage for a regulated output voltage of 5V and observe the
change in the duty cycle of the PWM waveform. Use Table 12.1 to record the
readings. Compare the readings with simulation results and plot the graph
between the input voltage and duty cycle. Is the plot linear?
0.7
1
V
V
V V
R R
R
V Vdutycycle
TP
TP
M
R
TP
J
TP
TP
R
C
209 207
209
205
207
209
20
201
203
204
201
213
out
ref
ref
out in
8
$
X
=
=
=
=
b
b
+