LXT386LE datasheet(23/78 Pages) INTEL

23 / 78 page

QUAD T1/E1/J1 Transceiver — LXT386

Datasheet

3.2

Receiver

The four receivers in the LXT386 are identical. The following paragraphs describe the operation of

one.

The twisted-pair input is received via a 1:2 step down transformer. Positive pulses are received at

RTIP, negative pulses at RRING. Recovered data is output at RPOS and RNEG in the bipolar mode

and at RDATA in the unipolar mode. The recovered clock is output at RCLK. RPOS/RNEG

validation relative to RCLK is pin selectable (CLKE).

The receive signal is processed through the peak detector and data slicers. The peak detector

samples the received signal and determines its maximum value. A percentage of the peak value is

provided to the data slicers as a threshold level to ensure optimum signal-to-noise ratio. For DSX-1

applications (line length inputs LEN2-0 from 011 to 111) the threshold is set to 70% (typical) of the

peak value. This threshold is maintained above the specified level for up to 15 successive zeros

over the range of specified operating conditions. For E1 applications (LEN2-0 = 000), the

threshold is 50% (typical).

The receiver is capable of accurately recovering signals with up to 12 dB of attenuation (from 2.4

V), corresponding to a received signal level of approximately 500 mV. Maximum line length is

1500 feet of ABAM cable (approximately 6 dB of attenuation). Regardless of received signal level,

the peak detectors are held above a minimum level of 0.150 V (typical) to provide immunity from

impulsive noise.

After processing through the data slicers, the received signal goes to the data and timing recovery

section. The data and timing recovery circuits provide an input jitter tolerance better than required

by Pub 62411 and ITU G.823, as shown in Test Specifications, Figure 33.

Depending on the options selected, recovered clock and data signals may be routed through the

jitter attenuator, through the B8ZS/HDB3/AMI decoder, and may be output to the framer as either

bipolar or unipolar data.

Figure 5. Pullup Resistor to RESET

LXT386LE

VCC

100

RESET

LXT386LE Datasheet(PDF) 23 Page - Intel Corporation