TPS54519 Datasheet, PDF (23/33 Pages) Texas Instruments – 2.95 V to 6 V Input, 5-A Synchronous Step Down SWIFT Converter

TPS54519
www.ti.com
SLVSAT3 – SEPTEMBER 2011
-G_PWRSTG
R3 = ^{10 20}
× ^Vout
gm_EA
V_REF
(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.
1
C5 =
2 × p × R3 × ^FCO
10
(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.
1
C4 =
2 × p × R3 × F_P
(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.
1
F_Z = _{2 × p × C10 × R6}
(39)
1
F_P = _{2 × p × C10 × R6 P R7}
(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.
1
C10 =
2 × p × R6 × F_CO ×
V_REF
V_OUT
(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
EFFICIENCY
vs
LOAD CURRENT
100
90
80
70
60
50
40
30
20
10
0
0 0.5 1 1.5 2 2.5 3 3.5
Output Current (A)
Figure 29.
V_IN = 3.3 V
V_IN = 5 V
4 4.5 5
G001
100
90
80
70
60
50
40
30
20
10
0
0.001
EFFICIENCY
vs
LOAD CURRENT
0.01
0.1
Output Current (A)
Figure 30.
V_IN = 3.3 V
V_IN = 5 V
1
G002
Copyright © 2011, Texas Instruments Incorporated
Product Folder Link(s): TPS54519
Submit Documentation Feedback
23