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, supports AMI/HDB3 waveform recovery, provides 32-bit or 128-bit crystal-less jitter attenuation, and operates with 3.3V supply. It is deployed in DSLAMs and IMA/WAN equipment for synchronous TDM transport over twisted-pair or coaxial lines.

For engineers reviewing the DS21Q50L datasheet, DS21Q50L pinout, DS21Q50L application, or DS21Q50L equivalent, key selection considerations include E1 compliance (ITU-T G.703/G.704/G.823), interleave bus operation up to 16.384MHz, per-channel loopback support, elastic-store slip buffering, and configurable parallel/serial host interface timing.

Technical Context

The DS21Q50L implements four fully independent E1 transceivers, each with dedicated clock/data recovery, framing (FAS/CAS/CCS/CRC4), and transmit waveshaping circuitry. Its analog front-end accepts ±2.5V AMI/HDB3 signals on 75Ω coax or 120Ω twisted-pair, with receive sensitivity from 0dB to –43dB.

It features a 4/8/16MHz clock synthesizer locked to any E1 line, dual-frame elastic-store buffers on receive paths, and hardware-selectable jitter attenuators placed in either transmit or receive data paths. The device supports interleaved PCM bus operation without external logic and includes PRBS generation/detection with error counting per channel.

Key Specifications

Pinout & Package

DS21Q50L is housed in a 100-pin LQFP package (14mm × 14mm), with dedicated analog and digital supply/ground domains, isolated receive/transmit analog sections, and four independent E1 channel interfaces.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS21Q50L, DS21Q55 offers wider temperature operation and expanded diagnostics but requires no layout changes, while MC21Q50 provides identical functionality under Microchip's branding and lifecycle management-both serve as drop-in alternatives for new or sustaining designs.

Availability

DS21Q50L is available at Aetrix Electronics and suitable for DSLAMs, WAN routers, IMA equipment, and telecom line cards requiring stable component supply, long-term manufacturability, and full ITU-T compliance.

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, industrial, and computing markets.

The DS21Q50L belongs to Maxim's telecom line interface product line, engineered specifically for carrier-grade E1/T1 physical layer termination in space-constrained, high-reliability network infrastructure.

FAQ

What is the operating temperature range for DS21Q50L?

The DS21Q50L is rated for commercial temperature operation from 0°C to +70°C. This range is specified in the ordering information section of the datasheet and applies to all electrical and timing parameters unless otherwise noted. DS21Q50L is not qualified for industrial or extended temperature use; for those environments, the DS21Q55 variant (–40°C to +85°C) is recommended. Thermal derating is not supported, and operation outside this range may result in undefined behavior or permanent damage to the DS21Q50L.

Does DS21Q50L support both FAS and CRC4 framing formats?

Yes, DS21Q50L supports frame alignment signal (FAS), channel-associated signaling (CAS), common-channel signaling (CCS), and CRC4 multiframe formats. The framers locate frame and multiframe boundaries and monitor for alarms in all these modes. Configuration is done via internal registers accessible through the parallel or serial port. DS21Q50L fully complies with ITU-T G.704 and G.706 for all supported framing types, and the device automatically adapts to incoming format without external intervention.

Can DS21Q50L drive 75Ω coaxial and 120Ω twisted-pair cables directly?

Yes, DS21Q50L generates G.703-compliant waveshapes for both 75Ω coaxial and 120Ω twisted-pair interfaces using its integrated transmit line drivers. The TRING/TTIP outputs provide differential analog signals with programmable line build-out (LBO) settings to match cable impedance and length. No external line transformers or amplifiers are required for standard E1 distances up to 2km on 22AWG twisted-pair or 655m on 75Ω coax - all necessary shaping and drive strength is implemented internally in the DS21Q50L.

How does the elastic store function in DS21Q50L improve system reliability?

The DS21Q50L implements a two-frame elastic store on each receive path to absorb phase and frequency mismatches between the recovered E1 clock and the asynchronous backplane system clock (SYSCLK). This prevents data loss due to buffer overflow/underflow during clock domain crossing. By dynamically inserting or deleting bits within the elastic buffer, DS21Q50L maintains continuous data flow even under transient clock instability - a critical capability in multi-E1 aggregation systems where line clocks are not synchronized. This feature is enabled per channel via register control.

Is DS21Q50L pin-compatible with DS21Q55?

Yes, DS21Q50L is pin-compatible with DS21Q55 - both use the identical 100-pin LQFP (14mm × 14mm) package and share the same pin assignments, power domains, and interface signaling. The DS21Q55 extends the temperature range and adds minor diagnostic enhancements, but requires no PCB layout changes or firmware modifications when substituted for DS21Q50L. Register maps, timing diagrams, and initialization sequences remain fully compatible, making DS21Q55 a direct upgrade path for designs needing extended thermal performance.