Datasheet
PTH08T255W Type C Capacitors
600
10000
6000
4000
900
C – Capacitance – mF
2
1
4
8
Transient – mV/A
3
700
800
1000
2000
5000
3000
8000
7000
9000
With TurboTrans
With TurboTrans
Without TurboTrans
Without TurboTrans
6
5
7
( )
( )
O
TT
O
1 C 4700
R 40 (k )
5 C 4700 1
-
= ´ W
´ -
(3)
PTH08T255W
www.ti.com
........................................................................................................................................................................................... SLTS290 – NOVEMBER 2008
12-V INPUT
Figure 8. Capacitor Type C,
5000 < C( µ F) × ESR(m Ω ) ≤ 10,000(e.g. OS-CON)
Table 5. Type C TurboTrans C
O
Values and Required R
TT
Selection Table
Transient Voltage Deviation (mV) 12 Volt Input
25% load step 50% load step 75% load step C
O
R
TT
(10 A) (20 A) (30 A) Minimum Required Output Required TurboTrans
Capacitance ( µ F) Resistor (k Ω )
65 130 195 1000 open
60 120 180 1050 280
50 100 150 1300 75.0
40 80 120 1700 31.6
30 60 90 2400 12.4
25 50 75 3000 6.49
20 40 60 3950 2.00
15 30 45 8000 short
R
TT
Resistor Selection
The TurboTrans resistor value, R
TT
can be determined from the TurboTrans programming Equation 3 .
Where C
O
is the total output capacitance in µ F. C
O
values greater than or equal to 4700 µ F require R
TT
to be a
short, 0 Ω . (Equation 3 results in a negative value for R
TT
when C
O
> 4700 µ F).
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 8 .
Copyright © 2008, Texas Instruments Incorporated 15
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