Analog Devices Inc./Maxim Integrated DS21Q50L+

Overview

DS21Q50L+ from Maxim Integrated is a quad E1 transceiver IC designed for high-density E1 line termination in telecom infrastructure. It integrates four independent E1 framer/transceiver channels, on-chip clock/data recovery for AMI/HDB3 waveforms, selectable 32-bit or 128-bit jitter attenuation, and supports 75Ω coax and 120Ω twisted-pair interfaces up to 2km. Used in DSLAMs and IMA/WAN equipment for synchronous TDM backplane interfacing.

For engineers reviewing the DS21Q50L+ datasheet, DS21Q50L+ pinout, DS21Q50L+ application, or DS21Q50L+ equivalent, this page provides verified technical context, pin-level circuit roles, real-world E1 framing behavior (FAS/CAS/CRC4), jitter attenuation placement options, and validated alternatives for E1 line interface design.

Technical Context

The DS21Q50L+ implements four fully independent E1 transceivers with separate transmit/receive clock domains, elastic-store slip buffers on receive paths, and hardware-configurable jitter attenuators assignable to either direction. Each channel supports G.703-compliant waveshaping, automatic cable-length adaptation (0–2km), and dual-mode framing (FAS/CAS or CCS/CRC4).

It features a 4/8/16MHz system clock synthesizer locked to any E1 line, interleaved PCM bus operation up to 16.384MHz, and parallel/serial host interface with register-mapped control. The device includes PRBS generation/detection, bipolar violation counting, and eight user-configurable output pins for status or control signaling.

Key Specifications

Pinout & Package

DS21Q50L+ is housed in a 100-pin LQFP package (14mm × 14mm) with dedicated analog/digital power and ground domains, separated receive/transmit analog sections, and multiplexed parallel/serial control interface.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS21Q50L+, DS21Q55+ offers extended thermal reliability without design changes, while SI5338-B-GM serves a fundamentally different clock-generation role and cannot replace DS21Q50L+'s E1 transceiver functionality.

Availability

DS21Q50L+ is available at Aetrix Electronics and suitable for DSLAMs, carrier-grade routers, IMA backhaul nodes, and WAN optimization appliances requiring stable component supply, long-term lifecycle support, and traceable sourcing for telecom infrastructure programs.

Supply support for DS21Q50L+ 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 solutions for communications, computing, and industrial markets.

The DS21Q50L+ belongs to Maxim's telecom line interface product line, engineered specifically for E1/E2 physical layer termination in space-constrained, high-channel-count telecom equipment.

FAQ

What is the maximum supported cable length for DS21Q50L+ on 22AWG twisted-pair?

The DS21Q50L+ supports E1 transmission and reception over 22AWG twisted-pair cables up to 2km in length. This is enabled by its adaptive receive sensitivity range (0dB to –43dB) and programmable line build-out (LBO) settings in the transmit analog section. The device automatically adjusts equalization and drive strength based on detected cable loss, eliminating manual calibration. DS21Q50L+ maintains G.703 compliance across this full range without external components.

Does DS21Q50L+ support both FAS and CRC4 framing modes?

Yes, DS21Q50L+ supports frame alignment signal (FAS), channel-associated signaling (CAS), common-channel signaling (CCS), and CRC4 multiframe formats. Configuration is done per channel via control registers-allowing mixed-mode operation across its four transceivers. The framers detect and lock to incoming FAS words or CRC4 codewords, and generate appropriate overhead in transmit mode per ITU-T G.704 and G.706 specifications. DS21Q50L+ fully complies with ETS 300 011 and ETS 300 233 framing requirements.

Can DS21Q50L+ operate without an external crystal?

Yes, DS21Q50L+ operates crystal-less due to its integrated 32-bit or 128-bit jitter attenuator and on-chip VCO/PLL for clock/data recovery. It recovers timing directly from the incoming AMI/HDB3 waveform and uses that recovered clock for internal synchronization. The device also includes a 4/8/16MHz clock synthesizer that locks to any active E1 line-eliminating need for external crystal oscillators or clock generators. DS21Q50L+ requires no external crystal to achieve full G.823 jitter performance.

How does the elastic store function in DS21Q50L+ improve system timing robustness?

The DS21Q50L+ implements a two-frame elastic-store buffer on each receive path to absorb phase and frequency differences between the recovered E1 clock (RCLK) and the asynchronous backplane system clock (SYSCLK). This prevents bit slips during clock domain crossing and ensures glitch-free data transfer to downstream processors. The elastic store dynamically inserts or deletes bits to maintain alignment-critical when aggregating multiple E1 lines with independent jitter profiles. DS21Q50L+'s elastic store is configurable per channel and supports both enabled and bypass modes.

Is DS21Q50L+ pin-compatible with DS21Q50LN?

Yes, DS21Q50L+ and DS21Q50LN are pin-compatible and share identical register maps, electrical characteristics, and functional behavior. The only difference is operating temperature range: DS21Q50L+ is rated for 0°C to +70°C, while DS21Q50LN extends to –40°C to +85°C. Both use the same 100-pin LQFP package and support identical configurations for framing, jitter attenuation, and IBO. DS21Q50L+ can be substituted with DS21Q50LN in existing designs without layout or firmware changes-subject to thermal validation.