Datasheet

C-Capacitance- Fm
Transient-mV/A
600
700
800
900
1000 2000 3000 4000 5000
6000
7000
8000
9000
10000
3
2
1
WithTurboTrans
WithoutTurboTrans
8
5
6
7
4
V =12V
I
C-Capacitance- Fm
Transient-mV/A
600
700
800
900
1000 2000 3000 4000 5000
6000
7000
8000
9000
10000
3
2
1
8
5
6
7
4
WithTurboTrans
WithoutTurboTrans
V =8V
I
R
TT
Resistor Selection
R =40
TT
´
kW
1-(C /3300)
O
5x(C /3300)-1
O
(2)
PTV08T250W
SLTS260E – OCTOBER 2005 – REVISED NOVEMBER 2008 .......................................................................................................................................... www.ti.com
Type B Capacitor Type B Capacitor
12 V Input 8 V Input
Figure 11. Cap Type B, 1000 ≤ C( µ F)xESR(m Ω ) ≤ 5000, Figure 12. Cap Type B, 1000 ≤ C( µ F)xESR(m Ω ) ≤ 5000,
(e.g. Polymer-Tantalum) (e.g. Polymer-Tantalum)
Table 3. Type B TurboTrans C
O
Values & Required R
TT
Selection Table
Transient Voltage Deviation (mV) 12 V Input 8 V Input
25% 50% 75% C
O
R
TT
C
O
R
TT
load step load step load step Minimum Required Required Minimum Required Required
(12.5 A) (25 A) (37.5 A) Output Capacitance TurboTrans Output Capacitance TurboTrans
( µ F) Resistor ( Ω ) ( µ F) Resistor ( Ω )
90 180 270 660 open 660 open
80 160 240 660 open 820 133 k
70 140 210 660 open 1000 56.2
60 120 180 880 95.3 k 1250 28.0 k
50 100 150 1200 30.9 k 1650 13.7 k
40 80 120 1800 10.5 k 2300 5.11 k
35 70 105 2300 4.99 k 2800 1.96 k
30 60 90 3050 909 3900 0
25 50 75 6900 0 9900 0
The TurboTrans resistor value, R
TT
can be determined from the TurboTrans programming equation, see
Equation 2 :
Where C
O
is the total output capacitance in µ F. C
O
values greater than or equal to 3300 µ F require R
TT
to be a
short, 0 Ω . (R
TT
results in a negative value when C
O
> 3300 µ F.)
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