Datasheet

)A1(
Z
R
R
R
1
A
)S(
V
V
VOL
FS
10
8
10
VOL
IN
OUT
+´++
=
–50
–40
–30
–20
0
10
20
30
50
0.1 1 10 100 1000
Crossover Frequency (kHz)
Gain (dB)
Phase (°)
Gain
Phase
–10
40
0
20
40
60
80
100
120
140
160
180
TPS40200
www.ti.com
SLUS659F FEBRUARY 2006REVISED MARCH 2012
where
Z
fs
is the parallel combination of C
7
in parallel with
the sum of R
8
and the impedance of C
8
.
A
VOL
is the open-loop gain of the error amplifier at
35 kHz, which is 44.6, or 33 db.
Figure 40 shows the result of the compensation. The crossover frequency is 35 kHz and the phase margin is 45
degrees. The response of the system is dominated by the ESR of the output capacitor and is exploited to
produce an essentially single-pole system with simple compensation.
Figure 40. Overall System Gain and Phase Response
Figure 40 also shows the phase boost that gives the system a crossover phase margin of 47°.
The bill of materials for this application is shown below. The efficiency and load regulation from boards built from
this design are shown in the following two figures. Gerber PC layout files and additional application information
are available from the factory.
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