Analog Devices Inc./Maxim Integrated DS21Q44T+

Overview

DS21Q44T+ from Maxim Integrated is an enhanced quad E1 framer IC designed for telecom line interface units and digital access cross-connect systems. It integrates four fully independent E1 framers supporting FAS, CAS, CCS, and CRC4 formats; features dual two-frame elastic stores per framer (up to 8.192MHz asynchronous backplane support); and includes an integral HDLC controller with 64-byte buffers configurable for Sa bits or DS0 operation.

For engineers reviewing the DS21Q44T+ datasheet, DS21Q44T+ pinout, DS21Q44T+ application, or DS21Q44T+ equivalent, key selection considerations include E1 framing compliance (ITU G.704/G.706/G.962/I.431, ETS 300 011/300 233), per-channel code insertion capability, IEEE 1149.1 JTAG support, and 3.3V supply with 5V-tolerant I/O.

Technical Context

The DS21Q44T+ implements four independent receive framer + elastic store + transmit formatter + elastic store chains, with no shared framing synchronizer. Each framer supports full E1 frame alignment (FAS), multiframe synchronization (CAS/CRC4), and alarm detection (AIS, RAI, RLOS, RRA, RUA1) with state-change interrupt generation.

Its dual elastic stores per framer operate independently-receive-side stores absorb phase/frequency differences between recovered E1 data (2.048MHz) and asynchronous backplane clocks up to 8.192MHz; transmit-side stores enable timing decoupling from backplane sources. The integrated HDLC controller handles Sa-bit or DS0-level data with 64-byte TX/RX buffers and programmable signaling reinsertion.

Key Specifications

Pinout & Package

DS21Q44T+ is housed in a 128-pin thin quad flat package (TQFP) with exposed thermal pad, optimized for telecom PCB layouts requiring signal integrity and thermal management in line card applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS21Q44TN+, DS21Q44T+ provides identical electrical and functional performance but targets commercial-temperature applications-reducing cost and simplifying thermal design where ambient stays within 0°C–70°C. Against DS21Q43+, DS21Q44T+ delivers measurable improvements in signaling flexibility, alarm responsiveness, and system-level integration via its expanded feature set.

Availability

DS21Q44T+ is available at Aetrix Electronics and suitable for telecom line cards, digital cross-connect systems, ISDN-PRI gateways, and enterprise PBX interface modules requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for DS21Q44T+ 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 DS21Q44T+ belongs to Maxim's telecom line interface product line, engineered specifically for E1/T1 framer applications in carrier-grade and enterprise infrastructure where standards compliance, timing precision, and multi-channel independence are critical.

FAQ

What is the operating temperature range for DS21Q44T+?

The DS21Q44T+ is specified for commercial temperature operation from 0°C to +70°C. This range aligns with standard indoor telecom equipment environments such as central office shelves and enterprise PBX racks. For extended temperature applications, the DS21Q44TN+ variant supports -40°C to +85°C and shares identical pinout and functionality with DS21Q44T+.

Does DS21Q44T+ support both CAS and CCS E1 framing modes?

Yes, DS21Q44T+ supports both Channel Associated Signaling (CAS) and Common Channel Signaling (CCS) E1 framing formats, along with FAS and CRC4 multiframe structures. It fully complies with ITU-T G.704 and ETSI ETS 300 011, enabling flexible deployment in legacy TDM networks using either signaling methodology without hardware change.

How does the dual elastic store architecture in DS21Q44T+ improve system design?

The dual two-frame elastic store per framer in DS21Q44T+ allows independent absorption of phase and frequency variations between recovered E1 data and asynchronous backplane clocks up to 8.192MHz. This eliminates external clock domain crossing logic, simplifies timing closure, and enables direct connection to FPGA or ASIC backplanes without jitter accumulation or data loss across all four E1 channels.

Is DS21Q44T+ pin-compatible with earlier Maxim quad framers?

DS21Q44T+ is pin-compatible with the DS21Q42 quad T1 framer in TQFP packaging, but not functionally interchangeable due to E1 vs. T1 framing differences. It is also software-compatible with DS21Q43, retaining the same register map while adding new features-enabling drop-in firmware upgrades without PCB redesign.

What JTAG capabilities does DS21Q44T+ provide?

DS21Q44T+ implements full IEEE 1149.1 boundary-scan architecture with dedicated JTRST, JTMS, JTCLK, JTDI, and JTDO pins. It supports device identification, interconnect testing, and in-system programming verification-critical for high-reliability telecom manufacturing and field diagnostics. The JTAG interface operates independently of the parallel control port and remains functional during normal framer operation.