Datasheet
1000
600
700
5000
4000
3000
2000
10000
6000
8
5
6
Without TurboTrans
With TurboTrans
800
900
7000
8000
9000
4
2
3
1
7
C - Capacitance - mF
Transient - mV/A
1000
600
700
5000
4000
3000
2000
10000
6000
8
5
6
Without TurboTrans
With TurboTrans
800
900
7000
8000
9000
4
2
3
1
7
C - Capacitance - mF
Transient - mV/A
( )
( )
O
TT
O
1 C 3300
R 40 (k )
5 C 3300 1
-
= ´ W
´ -
PTH08T250W
SLTS278G –NOVEMBER 2010–REVISED MARCH 2009
www.ti.com
PTH08T250W Type B Capacitors
12-V INPUT 5-V INPUT
Figure 12. Capacitor Type B, Figure 13. Capacitor Type B,
1000 < C(mF)×ESR(mΩ) ≤ 5000 (e.g. 1000 < C(mF)×ESR(mΩ) ≤ 5000 (e.g.
Polymer-Tantalum) Polymer-Tantalum)
Table 4. Type B TurboTrans C
O
Values and Required R
TT
Selection Table
Transient Voltage Deviation (mV) 12 Volt Input 5 Volt Input
25% load step 50% load step 75% load step C
O
R
TT
C
O
R
TT
(12.5 A) (25 A) (37.5 A) Minimum Required Minimum Required
Required Output TurboTrans Required Output TurboTrans
Capacitance (mF) Resistor (kΩ) Capacitance (mF) Resistor (kΩ)
100 200 300 660 open 660 open
85 170 255 660 open 750 226
75 150 225 800 143 870 93.1
60 120 180 1050 46.4 1150 34.8
50 100 150 1300 24.9 1450 18.7
40 70 105 1750 11.3 1950 8.45
30 60 90 2500 3.48 2800 1.87
25 50 75 3100 0.649 4000 short
R
TT
Resistor Selection
The TurboTrans resistor value, R
TT
can be determined from the TurboTrans programming Equation 2.
(2)
Where C
O
is the total output capacitance in mF. C
O
values greater than or equal to 3300 mF require R
TT
to be a
short, 0Ω. (Equation 2 results in a negative value for R
TT
when C
O
> 3300 mF.)
To ensure stability, a minimum amount of output capacitance is required for a given R
TT
resistor value. The value
of R
TT
must be calculated using the minimum required output capacitance determined from Figure 12 and
Figure 13.
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