Datasheet

C − Capacitance − µF
Transient − mV/A
1000
500 400 300 200
600 700 100
5000
4000
3000
2000
10000
6000
20
10
9
8
7
30
40
50
60
Without TurboTrans
With TurboTrans
C − Capacitance − µF
Transient − mV/A
1000
500 400 300 200 600 700 100
5000
4000
3000
2000
10000
6000
20
10
9
8
7
30
40
50
60
Without TurboTrans
With TurboTrans
R
TT
=40x
1-(C /1000)
O
5 x(C /1000)-1
O
(k )W
[]
PTH08T230W, PTH08T231W
SLTS265L –NOVEMBER 2005– REVISED AUGUST 2011 www.ti.com
PTH08T230W Type B Capacitors
12-V INPUT 5-V INPUT
Figure 14. Capacitor Type B, 1000 < C(μF) x Figure 15. Capacitor Type B, 1000 < C(μF) x
ESR(mΩ) ≤ 5000 ESR(mΩ) ≤ 5000
(e.g. Polymer-Tantalum) (e.g. Polymer-Tantalum)
Table 5. Type B TurboTrans C
O
Values and Required R
TT
Selection Table
Transient Voltage Deviation (mV) 12 V Input 5 V Input
C
O
R
TT
C
O
R
TT
25% load step 50% load step 75% load step Minimum Required Minimum Required
(1.5 A) (3 A) (4.5 A) Required Output TurboTrans Required Output TurboTrans
Capacitance (μF) Resistor (kΩ) Capacitance (μF) Resistor (kΩ)
75 150 225 200 open 200 open
60 120 180 260 100 270 82.5
50 100 150 320 45.3 330 41.2
40 80 120 420 21.0 430 19.6
30 60 90 600 8.06 610 7.68
25 50 75 740 3.83 760 3.40
20 40 60 980 0.205 1000 short
15 30 45 3800 short 4500 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 μF. C
O
values greater than or equal to 1000 μF require R
TT
to be
a short, 0 Ω.
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 the
capacitor transient response charts above.
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