Analog Devices Inc./Maxim Integrated DS2156L+

Overview

DS2156L+ from Maxim Integrated is a software-selectable T1/E1/J1 single-chip transceiver (SCT) with integrated line interface unit, framer, dual HDLC controllers, and configurable TDM or UTOPIA II backplane interface. It operates across 0°C to +70°C, supports G.703 E1 waveshapes for 75Ω/120Ω media, DSX-1 T1 line buildouts (-7.5dB to -22.5dB), and delivers 16.384MHz clock output synthesized to recovered network clock. Used in T1/E1 line cards and IMA-based ATM edge equipment.

For engineers reviewing the DS2156L+ datasheet, DS2156L+ pinout, DS2156L+ application, or DS2156L+ equivalent, key selection criteria include software-selectable T1/E1/J1 mode, crystal-less jitter attenuation, internal programmable termination (75Ω/100Ω/120Ω), dual elastic-store slip buffers, and Intel/Motorola bus-compatible 8-bit parallel control port.

Technical Context

The DS2156L+ implements a fully independent transmit/receive architecture with separate LIU sections for T1 and E1 waveform generation and 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 buffering and status reporting.

Backplane interfacing is user-configurable between TDM (multiplexed time-slot bus) and UTOPIA II (cell-based ATM interface), with support for fractional T1/E1 rates and programmable CLAV signaling. The jitter attenuator operates without external crystal, and the MCLK prescaler enables flexible clock synthesis from recovered network timing.

Key Specifications

Pinout & Package

DS2156L+ is housed in a 100-pin LQFP (14mm × 14mm, 0.5mm pitch) package with exposed thermal pad. Pin functions are defined for TDM/UTOPIA backplane, parallel control port (Intel/Motorola mode), LIU analog interface, JTAG test access, and supply/ground distribution.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS2155+, DS2156L+ adds UTOPIA II, CMI, and fractional rate support-enabling next-gen ATM and optical-E1 systems. Compared with MC2155P, DS2156L+ offers pin/software compatibility within Maxim's SCT family and superior integration of jitter attenuation and elastic storage.

Availability

DS2156L+ is available at Aetrix Electronics and suitable for T1/E1 line cards, inverse multiplexing over ATM (IMA) systems, and carrier-grade add-drop multiplexers requiring stable component supply, RoHS-compliant packaging, and long-term industrial temperature support.

Supply support for DS2156L+ 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 semiconductor company specializing in high-performance analog, mixed-signal, and RF ICs for communications, computing, and industrial applications.

The DS2156L+ belongs to Maxim's Single-Chip Transceiver (SCT) product line, designed specifically for carrier-class T1/E1/J1 physical layer interfacing with integrated framer, HDLC, and flexible backplane connectivity.

FAQ

What is the operating temperature range for DS2156L+?

The DS2156L+ is rated for commercial temperature operation from 0°C to +70°C. This range is validated per Maxim's datasheet specifications and applies to all electrical and timing parameters under normal bias conditions. The "+" suffix confirms lead-free/RoHS-compliant packaging. DS2156L+ is not rated for extended industrial temperatures; for -40°C to +85°C operation, DS2156LN+ must be selected instead.

Does DS2156L+ support both TDM and UTOPIA II backplane interfaces simultaneously?

No, DS2156L+ supports either TDM or UTOPIA II backplane interface-not both concurrently. Selection is made at power-up via configuration pins (MODE0/MODE1) and locked in firmware. The interface choice determines pin function allocation (e.g., TD0–TD7 vs. UTXCLK/URXCLK), and switching requires hardware reset. This design prevents signal contention and ensures deterministic timing behavior per application requirement.

How does the crystal-less jitter attenuator in DS2156L+ function without an external crystal?

The DS2156L+ jitter attenuator uses a digitally controlled loop that locks to the incoming network clock (T1 or E1), filters jitter using an internal DLL-based phase-locked structure, and regenerates a clean local clock. It requires no external crystal or reference oscillator-relying solely on the recovered network timing. This is confirmed in Section 23.5 of the DS2156 datasheet and eliminates BOM cost and layout area associated with crystal components.

Is DS2156L+ pin-compatible with DS2155+?

Yes, DS2156L+ is pin-compatible and software-compatible with DS2155+. Both use identical 100-pin LQFP packaging, matching pin assignments for power, ground, parallel port, LIU analog I/O, and JTAG. Firmware developed for DS2155+ runs unmodified on DS2156L+, though new features (UTOPIA II, CMI, fractional rates) require updated register writes. This compatibility is explicitly stated in the General Description section of the DS2156 datasheet.

What termination resistances are supported internally by DS2156L+ for E1 interfaces?

DS2156L+ supports programmable internal termination of 75Ω, 100Ω, and 120Ω on both transmit and receive sides for E1 interfaces. These values match common E1 cabling standards: 75Ω for coaxial and 120Ω for twisted-pair installations. Termination is configured per-channel via LIU control registers (Section 23.7), eliminating need for external resistor networks and enabling runtime adaptation to different physical layer topologies.