Datasheet

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    
SLLS428F − JUNE 2000 − REVISED JANUARY 2004
21
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
recommended values of external resistors (1% tolerance)
PARAMETER TEST CONDITIONS RECOMMENDED UNIT
R
(t)
, Termination resistor
50 Ω environment 50
Ω
R
(t)
, Termination resistor
75 Ω environment 75
Ω
R
(REF)
, Reference resistor
50 Ω environment 200
Ω
R
(REF)
, Reference resistor
75 Ω environment 300
Ω
RREF − Resistor Reference − Ω
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
100 150 200 250 300
VOLTAGE
vs
RESISTOR REFERENCE
VODP at 75 Ω
VODD at 50 Ω
VODD at 75 Ω
VODP at 50 Ω
VODP or VODD − V
Figure 14. Differential Transmitter Voltage
choosing RREF resistor values
TLK1501 offers the flexibility to customize the voltage swing and transmission line termination by adjusting the
reference resistor, RREF, and termination resistor, R
t
. By choosing particular resistor values, the system can
be optimized for a particular transmission line impedance, length, and controlling the output swing for EMI and
attenuation concerns. Refer to Figure 14 to determine the nominal voltage swing and driver current as a function
of resistor values. It is recommended that 1% tolerance resistors be used. Refer to Figure 15 for high-speed
I/O directly coupled mode and Figure 16 for high-speed I/O ac-coupled mode.