TLK2501 Datasheet, PDF (20/25 Pages) Texas Instruments – 1.5 TO 2.5 GBPS TRANSCEIVER

TLK2501
1.5 TO 2.5 GBPS TRANSCEIVER
SLLS427D − AUGUST 2000 − REVISED JULY 2003
APPLICATION INFORMATION
recommended values of external resistors (1% tolerance)
PARAMETER
R(t), Termination resistor
R(REF), Reference resistor
TEST CONDITIONS
50 Ω environment
75 Ω environment
50 Ω environment
75 Ω environment
RECOMMENDED
50
75
200
300
UNIT
Ω
Ω
VOLTAGE
vs
RESISTOR REFERENCE
2.0
1.8
VODD at 75 Ω
1.6
VODP at 75 Ω
1.4
1.2
VODD at 50 Ω
1.0
0.8
VODP at 50 Ω
0.6
100
150
200
250
300
RREF − Resistor Reference − Ω
Figure 14. Differential Transmitter Voltage
choosing RREF resistor values
TLK2501 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.
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