LTC1345 LINER [Linear Technology], LTC1345 Datasheet - Page 7

• Manufacturer Part Number: LTC1345
• Description: Single Supply V.35 Transceiver
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
Review of CCITT Recommendation V.35
Electrical Specifications
V.35 is a CCITT recommendation for synchronous data
transmission via modems. Appendix 2 of the recommen-
dation describes the electrical specifications which are
summarized below:
1. The interface cable is balanced twisted-pair with 80 to
120 impedance.
2. The transmitter’s source impedance is between 50 and
150 .
3. The transmitter’s resistance between shorted terminals
and ground is 150
4. When terminated by a 100 resistive load, the terminal-
to-terminal voltage should be 0.55V 20%.
5. The transmitter’s rise time should be less than 1% of the
signal pulse or 40ns, whichever is greater.
6. The common-mode voltage at the transmitter output
should not exceed 0.6V.
7. The receiver impedance is 100
8. The receiver impedance to ground is 150
9. The transmitter or receiver should not be damaged by
connection to earth ground, short-circuiting, or cross
connection to other lines.
10. No data errors should occur with 2V common-mode
change at either the transmitter or receiver, or 4V ground
potential difference between transmitter and receiver.
U
15 .
U
W
10 .
U
15 .
Cable Termination
Each end of the cable connected to an LTC1345 must be
terminated by either one of two electrically equivalent
external Y or resistor networks for proper operation. The
Y-termination has two series connected 50 resistors and
a 125 resistor connected between ground and the center
tap of the two 50 resistors as shown in Figure 6A.
The alternative -termination has a 120 resistor across
the twisted wires and two 300 resistors between each
wire and ground as shown in Figure 6B. Standard 1/8W,
5% surface mount resistors can be used for the termination
network. To maintain the proper differential output swing,
the resistor tolerance must be 5% or less. A termination
network that combines all the resistors into an SO-14
package is available from:
BI Technologies (Formerly Beckman Industrial)
Resistor Networks
4200 Bonita Place
Fullerton, CA 92635
Phone: [phone]
FAX: [phone]
Part #: BI Technologies 627T500/1250 (SOIC)
899TR50/125 (DIP)
Figure 6. Y and
120
50
50
Termination Networks
A
B
300
300
125
LTC1345
LTC1345 • F06
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