DJLXT380LE.B4 Cortina Systems Inc, DJLXT380LE.B4 Datasheet - Page 23

• Manufacturer Part Number: DJLXT380LE.B4
• Manufacturer: Cortina Systems Inc

Specifications of DJLXT380LE.B4

• Lead Free Status / RoHS Status: Not Compliant

2.4
2.4.1
Datasheet
Figure 5. 50% AMI Coding
Transmitter
The eight low power transmitters of the LXT380 are identical.
Transmit data applied to TPOS/TNEG is clocked serially into the device. Input synchronization is
supplied by the transmit clock (TCLK). The TPOS/TNEG inputs are sampled on the falling edge of
TCLK. Refer to MCLK and TCLK timing characteristics.
Unipolar I/O and HDB3 encoding/decoding is selected by pulling TNEG High for more than 16
TCLK clock cycles.
Each output driver is supplied by a separate power supply: TVCC and TGND. This allows each
transmitter power supply to be de-coupled independently. The LXT380 transmits data as a 50%
AMI line code as shown in
The transmit pulse shaper is bypassed if no MCLK is supplied while TCLK is pulled High. In this
case TPOS and TNEG control the pulse width and polarity on TTIP and TRING. With MCLK
supplied and TCLK pulled High the driver enters TAOS (Transmit All Ones pattern). TAOS is
inhibited during Remote Loopback.
Transmit Pulse Shaping
The transmitted pulse shape is internally generated using a high speed D/A converter. Shaped
pulses are further applied to the AMI line driver for transmission onto the line at TTIP and TRING.
The line driver provides a constant low output impedance regardless of whether it is driving marks,
spaces or if it is in transition. This well controlled dynamic impedance provides excellent return
loss when used with external precision resistors (± 1% accuracy) in series with the transformer.
The LXT380 produces 2.048 MHz pulses for both 75
twisted-pair (3.0 V) lines through an output transformer with a 1:2 step up pulse transformer and 11
output driver dynamically adjusts its output pulse amplitude.
TRING
TTIP
series resistors. No transmit component changes are required in 75
Bit Cell
1
Figure
0
5.
1
Octal E1 G.703 Transceiver — LXT380
coaxial (2.37 V) or 120
or 120
operation as the
shielded
23