LXT386LE datasheet(26/78 Pages) INTEL

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LXT386 — QUAD T1/E1/J1 Transceiver

Datasheet

Each output driver is supplied by a separate power supply (TVCC and TGND). 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). Note that the TAOS generator uses

MCLK as a timing reference. In order to assure that the output frequency is within specification

limits, MCLK must have the applicable stability.TAOS is inhibited during Remote Loopback.

3.3.1

Transmit Pulse Shaping

The transmitted pulse shape is internally generated using a high speed D/A converter. Shaped

pulses are further applied to the 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.

3.3.1.1

Hardware Mode

In hardware mode, pins LEN0-2 determine the pulse shaping as described in Table 2. The LEN

settings also determine whether the operating mode is T1 or E1. Note that in T1 operation mode, all

four ports will share the same pulse shaping setting. Independent pulse shaping for each channel is

available in host mode

3.3.1.2

Host Mode

In Host Mode, the contents of the Pulse Shaping Data Register (PSDAT) determines the shape of

pulse output at TTIP/TRING. Refer to Table 24 and Table 25.

Figure 6. 50% AMI Encoding

TTIP

TRING

Bit Cell

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