Datasheet
( )
Z 2
PZ 2 P 1 Z 2 P Z 2 Z 2
1 1
f
2 R R C 2 R C
= »
p ´ + ´ p ´ ´
Z1
Z1 PZ1
1
f
2 R C
=
p ´ ´
P 2 Z 2
P 2
PZ 2 P 2 Z 2 PZ 2 P 2
C C
1
f
2 R C C 2 R C
+
= »
p ´ ´ ´ p ´ ´
P1
P1 PZ1
1
f
2 R C
=
p ´ ´
f
f
PZ2 Z1 P1
c PZ1
Z1 P1
C PZ1
1
R R R
2 C
Gain
1
R R
2 C
æ ö
æ ö
´ + +
ç ÷
ç ÷
ç ÷
p ´
è ø
è ø
=
æ ö
+
ç ÷
p ´
è ø
SE T
0.591 51k
R 24.9 k
1.8 0.591
´ W
= = W
-
( )
( )
REGF Z1
SET
OUT REF
V R
R
V V
´
=
-
−20
100 1 k 1 M
−10
0
10
20
30
40
f − Frequency − Hz
Gain − dB
f
P2
f
P1
f
Z2
f
Z1
High−Frequency
Gain
2
3
TPS40195
R
SET
R
PZ2
C
Z2
C
P2
FB
COMP
R
Z1
R
P1
C
PZ1
VOUT
TPS40195
SLUS720E –FEBRUARY 2007–REVISED JULY 2012
www.ti.com
Figure 26. Type III Compensation Schematic Figure 27. Type-III Compensation Network Typical
Bode Plot
The output voltage, the high-frequency gain and the break (pole and zero) frequencies are calculated using the
following equations.
(43)
(44)
(45)
(46)
(47)
(48)
(49)
Steps in closing the feedback loop.
1. Place one zero well below the L-C double pole at 5.8 kHz (f
Z1
=2.1 kHz)
2. Place the second zero near the double pole f
Z2
at 5.8 kHz.
3. Place one pole well above the desired cross over frequency, selected as one sixth the switching frequency,
f
CO1
= 50 kHz, f
P1
= 300 kHz
28 Copyright © 2007–2012, Texas Instruments Incorporated