DS2148 データシートの表示（PDF） - Maxim Integrated

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DS2148

5V E1/T1/J1 Line Interface Unit

Maxim Integrated 

DS2148/DS21Q48

1 DETAILED DESCRIPTION

The DS2148 is a complete selectable E1 or T1 Line Interface Unit (LIU) for short- and long-haul

applications. Throughout the data sheet, J1 is represented wherever T1 exists. Receive sensitivity adjusts

automatically to the incoming signal and can be programmed for 0dB to 12dB or 0dB to 43dB for E1

applications and 0dB to 30dB or 0dB to 36dB for T1 applications. The device can generate the necessary

G.703 E1 waveshapes in 75Ω or 120Ω applications and DSX-1 line built-outs or CSU line built-outs of

0dB, -7.5dB, -15dB, and -22.5dB for T1 applications. The crystal-less onboard jitter attenuator requires

only a 2.048MHz MCLK for both E1 and T1 applications (with the option of using a 1.544MHz MCLK

in T1 applications). The jitter attenuator FIFO is selectable to either 32 bits or 128 bits in depth and can

be placed in either the transmit or receive data paths. An X 2.048MHz output clock synthesized to RCLK

is available for use as a backplane system clock (where n = 1, 2, 4, or 8). The DS2148 has diagnostic

capabilities such as loopbacks and PRBS pattern generation/detection. 16-bit loop-up and loop-down

codes can be generated and detected. The device can be controlled via an 8-bit parallel muxed or

nonmuxed port, serial port or used in hardware mode. The device fully meets all of the latest E1 and T1

specifications including ANSI T1.403-1999, ANSI T1.408, AT&T TR 62411, ITU G.703, G.704, G.706,

G.736, G.775, G.823, I.431, O.151, O.161, ETSI ETS 300 166, JTG.703, JTI.431, JJ-20.1, TBR12,

TBR13, and CTR4.

1.1 Function Description

The analog AMI/HDB3 waveform off the E1 line or the AMI/B8ZS waveform off the T1 line is

transformer coupled into the RTIP and RRING pins of the DS2148. The user has the option to use

internal software-selectable receive-side termination for 75Ω/100Ω/120Ω applications or external

termination. The device recovers clock and data from the analog signal and passes it through the jitter

attenuation MUX outputting the received line clock at RCLK and bipolar or NRZ data at RPOS and

RNEG. The DS2148 contains an active filter that reconstructs the analog-received signal for the nonlinear

losses that occur in transmission. The receive circuitry also is configurable for various monitor

applications. The device has a usable receive sensitivity of 0dB to -43dB (E1) and 0dB to -36dB (T1),

which allows the device to operate on 0.63mm (22AWG) cables up to 2.5km (E1) and 6k feet (T1) in

length. Data input at TPOS and TNEG is sent via the jitter attenuation MUX to the waveshaping circuitry

and line driver. The DS2148 will drive the E1 or T1 line from the TTIP and TRING pins via a coupling

transformer. The line driver can handle both CEPT 30/ISDN-PRI lines for E1 and long-haul (CSU) or

short-haul (DSX-1) lines for T1.

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