WJLXT384LE.B1-868635 Cortina Systems Inc, WJLXT384LE.B1-868635 Datasheet - Page 53

• Manufacturer Part Number: WJLXT384LE.B1-868635
• Manufacturer: Cortina Systems Inc

Specifications of WJLXT384LE.B1-868635

• Screening Level: Industrial
• Mounting: Surface Mount
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Lead Free Status / RoHS Status: Compliant

LXT384 Transceiver
Datasheet
248994, Revision 6.0
30 January 2008
6.4.2.4
6.4.3
Note:
6.4.4
6.4.4.1
6.4.4.2
6.5
Cortina Systems
Power Sequencing
For the LXT384 Transceiver, sequence TVCC first, then VCC second or at the same time
as TVCC, to prevent excessive current draw.
Transmitter Outputs
A transmitter transmits output signals as follows:
If TCLK is not supplied, the transmitter is in a powered-down state and the TTIP and TRING
outputs are held in a low-power high-impedance tristate.
Transmitter Output Driver Power and Grounds
Each output driver is supplied by its own separate TVCC and TGND pins. The TVCC pins
can be either 3.3 V or 5 V nominal. The LXT384 Transceiver drives either a 75 Ω coaxial
cable or a 120 Ω twisted-pair cable.
For output drive short-circuit protection, see
6.4.4.1 Transmit Output Standard Power Options
The LXT384 Transceiver standard option uses a 1:2 transformer with two R
resistors. This power option has more margin for return loss, compared to the low-power
option discussed in the following section.
6.4.4.2 Transmitter Output Low-Power Options
The LXT384 Transceiver has a low-power option that meets all other specifications, with a
built-in safety margin. This option allows a different turns ratio so that power can be saved
on the LXT384 Transceiver power dissipation. To achieve this low-power option, select the
turns ratio to 1:1.7 and change the R
Line-Interface Protection
Figure 6
operation, Cortina strongly recommends these line-interface protection elements.) For the
appropriate values and tolerances of devices used with line-interface protection circuitry,
see
®
1. Through a step-up transformer, a transmitter transmits an output signal, typically to
2. One polarity of the output signal (the positive pulse) is transmitted at TTIP, and the other
• Receive side. Two 1 k Ω resistors protect the receiver against current surges that can
• Transmit side. Resistors R
LXT384 Octal T1/E1/J1 Short-Haul PCM Transceiver with Jitter Attenuation (JA)
either a twisted-pair or a coaxial cable. (For transformer specifications, see
and
polarity (the negative pulse) is transmitted at TRING.
couple into the LXT384 Transceiver. Due to the high receiver impedance (typically
70 k Ω), these resistors do not affect the receiver sensitivity.
line surges. To protect the LXT384 Transceiver output driver from surge currents in
excess of 100 mA, a transient voltage suppressor TVS1 (such as Teccor P0080S) is
required.
Table
Section 12.0, Line-Interface-Unit Circuit
shows circuitry for line-interface protection. (While not mandatory for normal
72.
T
and Schottky diodes D1-4 protect the output drivers from
T
resistor to 10 Ω. (See
Section 6.5, Line-Interface
Specifications.)
TM
TM
Figure 6
6.5 Line-Interface Protection
and
Protection.
Table
T
= 11 Ω
Figure 6
20.)
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