lxt384 Intel Corporation, lxt384 Datasheet - Page 53

• Manufacturer Part Number: lxt384
• Description: Octal T1/e1/j1 Short Haul Transceiver
• Manufacturer: Intel Corporation

6.4.3
Document Number: 248994
Revision Number: 004
Revision Date: September 22, 2005
Note: If TCLK is not supplied, the transmitter is in a powered-down state and the TTIP and TRING
6.4.2.3
6.4.2.4
The output driver power supply (TVCC pins) can be either 3.3V or 5V nominal.
The Channel 4 (TVCC4) power supply pin sets 3.3V or 5.0V transmit operation. See
Removing the series resistors for T1 applications with TVCC=3.3V, improves the power
consumption of the device.
However, series resistors in the transmit configuration improve the transmit return loss
performance. Good transmit return loss performance minimizes reflections in harsh cable
environments. In addition, series resistors provide protection against surges coupled to the device.
The resistors should be used in systems requiring protection switching without external relays.
Refer to
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:
outputs are held in a low-power high-impedance tristate.
1. Through a step-up transformer, a transmitter transmits an output signal, typically to either a
2. One polarity of the output signal (the positive pulse) is transmitted at TTIP, and the other
•
•
When TVCC=5V, theLXT384 Transceiver drives both E1 (75Ω/120Ω) and T1 (100Ω) lines
through a 1:2 transformer and 11Ω/9.1Ω series resistors.
When TVCC=3.3V, the LXT384 Transceiver drives E1 (75Ω/120Ω) lines through a 1:2
transformer and 11Ω series resistor. Use a configuration with a 1:2 transformer and without
series resistors to drive T1 100Ω lines.
twisted-pair or a coaxial cable. (For transformer specifications, see
“Line-Interface-Unit Circuit
polarity (the negative pulse) is transmitted at TRING.
Figure 6
Output Driver Power Supply
Power Sequencing
for the recommended external line circuitry.
Specifications”.)
Intel
®
LXT384 Octal T1/E1/J1 S/H PCM Transceiver with JA
Figure 6
and
Chapter 12.0,
Table
21.
53