Datasheet

f − Frequency − kHz
−60
−50
−40
−30
−20
−10
0
10
20
30
Gain − dB
G028
0.1 1 10 1k100
ESR Zero
Double Pole
ESR = 0.16 Ω
Slope = –20 dB/Decade
FB
COMP
TPS40077
SS
6
7
8
V
OUT
R
P1
R
Z1
R
PZ2
R
SET
C
PZ1
C
Z2
C
P2
S0240-01
TPS40077
www.ti.com ..................................................................................................................................................... SLUS714D – JANUARY 2007 – REVISED APRIL 2009
Figure 31. PWM and LC Filter Gain
The next step is to establish the required compensation gain to achieve the desired overall system response.
The target response is to have the crossover frequency between 1/9 and 1/5 times the switching frequency, in
order to have a phase margin greater than 45 ° and a gain margin greater than 6 dB.
A type-III compensation network, shown in Figure 32 , was used for this design. This network gives the best
overall flexibility for compensating the converter.
Figure 32. Type-III Compensation With the TPS40077
A typical Bode plot for this type of compensation network is shown in Figure 33 .
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