Datasheet

× p × × ×
REF
CO
OUT
1
C10 =
V
2 R6 F
V
× p × × P
P
1
F =
2 C10 R6 R7
× p × ×
Z
1
F =
2 C10 R6
× p × ×
P
1
C4 =
2 R3 F
× p × ×
CO
1
C5 =
F
2 R3
10
-
×
PWRSTG
G
20
out
EA REF
V
10
R3 =
gm V
TPS54519
SLVSAT3A –SEPTEMBER 2011–REVISED DECEMBER 2013 www.ti.com
(36)
To maximize phase gain, the compensator zero is placed one decade below the crossover frequency of 70 kHz.
The required value for C5 is given by Equation 37.
(37)
To maximize phase gain the high frequency pole is not implemented and C4 is not populated. The pole can be
useful to offset the ESR of aluminum electrolytic output capacitors. If desired the value for C4 can be calculated
from Equation 38.
(38)
For maximum phase boost, the pole frequency F
P
will typically be one decade above the intended crossover
frequency F
CO
.
The feed forward capacitor C10, is used to increase the phase boost at crossover above what is normally
available from Type II compensation. It places an additional zero/pole pair located at Equation 39 and
Equation 40.
(39)
(40)
This zero and pole pair is not independent. Once the zero location is chosen, the pole is fixed as well. For
optimum performance, the zero and pole should be located symmetrically about the intended crossover
frequency. The required value for C10 can calculated from Equation 41.
(41)
For this design the calculated values for the compensation components are R3 = 23.8 kΩ ,C5 = 959 pF and C10
= 197 pF. Using standard values, the compensation components are R3 = 23.7 kΩ ,C5 = 1000 pF and C10 =
220 pF.
APPLICATION CURVES
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