Datasheet LXT304APE, LXT304ANE Datasheet (Level One Communications)

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The LXT304A is a fully integrated low-power transceiver
for both North American 1.544 Mbps (T1), and Interna­tional 2.048 Mbps (E1) applications. It features a constant
low output impedance transmitter allowing for high trans­mitter return loss in T1/E1 applications. Transmit pulse
shapes (DSX-1 or E1) are selectable for various line
lengths and cable types.

The LXT304A provides receive jitter attenuation starting
at 3 Hz, and is microprocessor controllable through a serial
interface.

It offers a variety of diagnostic features including transmit
and receive monitoring. The device incorporates an on­chip crystal oscillator, and also accepts digital clock inputs.
It uses an advanced double-poly, double-metal CMOS pr o­cess and requires only a single 5-volt power supply.

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rate provides clock stabilization. Refer to Application
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The LXT304A transmits data as a 50% AMI line code as
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Rt resistors in line with the transmit transformer to provide
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LXT304A is shown in Hardware Mode with a typical E1/

CRC4 Framer. The hard-wired control lines for TAOS,
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LLOOP and RLOOP lines are also tied to a single control
for the Reset function. This configuration is illustrated
with a crystal in place to enable the LXT304A Jitter Atten­uation Loop, and a single power supply bus.

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Existing D4 Channel Bank architectures frequently em­ploy: (1) a plug-in card for T1 pulse generation (6.0 V
peak); and (2) a separate card for pulse shaping and Line
Build-Out (LBO). The LXT304A integ rates t he fun ctions
of both cards on a single chip producing a DSX-1 compat­ible, 3.0 V peak output pulse with a standard transformer.
In new designs, the LXT304A can replace two cards with
one. However, the LXT304A is also compatible with ex-

isting dual-card architectures. With an appropriate output
transformer, the LXT304A can produce full 6.0 V peak am­plitude pulses suitable for D4 Ch annel Bank applications
with separate pulse shaping/LBO cards.

To achieve the 6.0 V peak output, the FCC Part 68-010
Equalizer Code setting is used. (EC = 010.) With the stan­dard 1:1.15 transformer, this code produces a 3.0 V peak
pulse. However, doubling th e transformer turns ratio to
1:2.30 produces the desired 6.0 V peak pulse .

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1.Transformer turns ratio accuracy is ± 2%.

2.Rr and Rt values are ± 1%.

3.Typical return loss, 51 kHz to 3.072 MHz ban d.

4.D4 Channel Bank application.

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4.Ex cept MTIP and MRING ILL = ± 50 µA.

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5.Guaranteed by design.

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