Analog Devices Inc./Maxim Integrated DS2155LN+

Overview

DS2155LN+ from Maxim Integrated is a software-selectable T1/E1/J1 single-chip transceiver (SCT) integrating line interface unit (LIU), framer, dual HDLC controllers, and TDM backplane interface. It supports -40°C to +85°C operation in 100-pin LQFP, delivers crystal-less jitter attenuation, programmable 75Ω/100Ω/120Ω termination, and 16.384MHz backplane clock synthesis locked to recovered network clock - deployed in carrier-grade line cards and add-drop multiplexers.

For engineers reviewing the DS2155LN+ datasheet, DS2155LN+ pinout, DS2155LN+ application, or DS2155LN+ equivalent, key selection criteria include T1/E1/J1 protocol flexibility, independent transmit/receive path control, dual elastic-store slip buffers for asynchronous backplanes, CMI coding support for optical interfaces, and software-selectable line buildouts (-7.5dB/-15dB/-22.5dB for T1; G.703 for E1).

Technical Context

The DS2155LN+ implements a fully integrated T1/E1/J1 physical layer transceiver with separate analog LIU sections for transmit waveshaping and receive clock/data recovery. Its framer supports both T1 D4/ESF and E1 PCM-30/PCM-31 formats, while dual HDLC controllers handle channelized data encapsulation with FIFO-based packet buffering.

It features a crystal-less jitter attenuator compliant with ITU-T G.823/G.824 for long-haul timing stability, and its TDM backplane interface operates up to 16.384MHz with dual two-frame elastic stores enabling slip-tolerant connection to asynchronous system buses - all controlled via an 8-bit parallel port configurable for Intel or Motorola bus timing.

Key Specifications

Pinout & Package

DS2155LN+ is housed in a 100-pin LQFP package (56-G5002-000), with exposed thermal pad for enhanced heat dissipation in high-density telecom applications. Pin functions are grouped into transmit interface, receive interface, parallel control port (8-bit Intel/Motorola configurable), extended system information bus (ESIB), user output pins, JTAG test access, line interface, and supply domains.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar T1/E1 transceiver applications.

Compared with DS2156LN+, DS2155LN+ provides identical core functionality but lacks later-generation E1 CAS enhancements and marginally relaxed jitter specs; compared with MC25210ILF, DS2155LN+ delivers full T1/E1/J1 convergence, integrated HDLC, and smaller footprint - reducing design complexity and time-to-market.

Availability

DS2155LN+ is available at Aetrix Electronics and suitable for telecom line cards, carrier-grade routers, and add-drop multiplexers requiring stable component supply across industrial temperature ranges and long product lifecycles.

Supply support for DS2155LN+ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) is a U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and RF ICs for communications, computing, and industrial markets.

The DS2155LN+ belongs to Maxim's telecom transceiver product line, engineered specifically for carrier-class T1/E1/J1 line interface applications demanding protocol flexibility, jitter resilience, and system-level integration in space-constrained platforms.

FAQ

What protocols does the DS2155LN+ support, and how is mode selection implemented?

The DS2155LN+ supports T1 (1.544Mbps), E1 (2.048Mbps), and J1 (1.544Mbps) protocols through software configuration via its parallel control port registers. Mode selection is performed at initialization by writing to the master mode register (MMR), which configures the framer, LIU, and HDLC controllers for the target standard - no hardware changes or external jumpers are required. This enables dynamic reconfiguration in field-deployed systems.

Does the DS2155LN+ require an external crystal oscillator for jitter attenuation?

No, the DS2155LN+ incorporates a crystal-less jitter attenuator meeting ITU-T G.823 (T1) and G.824 (E1) masks using an internal PLL and loop filter. It recovers timing directly from the incoming line signal and generates a clean, low-jitter clock for internal logic and backplane output - eliminating the need for an external crystal and associated load capacitors, reducing BOM count and board area.

What is the function of the dual elastic-store slip buffers in the DS2155LN+?

The DS2155LN+ includes two independent two-frame elastic-store slip buffers - one for receive and one for transmit - that absorb timing differences between the recovered network clock and the local backplane clock domain. They enable reliable TDM data transfer across asynchronous backplanes operating up to 16.384MHz, preventing data loss during clock slips without requiring external FIFOs or complex clock-domain crossing logic.

How does the DS2155LN+ handle line termination for different cable types?

The DS2155LN+ provides software-selectable termination resistors (75Ω, 100Ω, or 120Ω) on both transmit and receive sides, configurable per channel via LIU control registers. This supports coaxial (75Ω), twisted-pair (120Ω), and hybrid (100Ω) media without external resistor networks - simplifying design for multi-standard deployments and enabling field reconfiguration via firmware update.

Is the DS2155LN+ pin-compatible with other devices in the same family?

Yes, the DS2155LN+ is pin- and software-compatible with the DS2156LN+, allowing drop-in replacement in existing designs. Both share identical 100-pin LQFP packaging, register map, and parallel port timing. However, the DS2156LN+ adds enhanced E1 CAS handling and improved jitter performance - making it suitable for new designs where those features are critical.