Analog Devices Inc./Maxim Integrated DS21FT44N+

Overview

DS21FT44N+ from Maxim Integrated is a 12-channel E1 framer multichip module (MCM) integrating three DS21Q44 quad-framer die in a single 300-pin BGA package. It supports full E1 framing (2.048 Mbps per channel), IEEE 1149.1 JTAG boundary scan, and operates across –40°C to +85°C. It serves as the core framer IC in high-density telecom line cards for DSLAMs and multiplexers.

For engineers reviewing the DS21FT44N+ datasheet, DS21FT44N+ pinout, DS21FT44N+ application, or DS21FT44N+ equivalent, key selection considerations include its 12-channel E1 framing capability, industrial temperature range, JTAG test support, 300-pin BGA footprint compatibility with DS21FT42, and absence of the fourth framer block (no RLOS/RLINK/TLCLK signals).

Technical Context

The DS21FT44N+ implements a 4×3 MCM architecture-three identical DS21Q44 quad-framer die sharing common control logic and bus interface. Each framer handles independent E1 streams with full G.704/G.706 compliance, HDLC-based Sa/Si bit processing, and elastic store-based clock recovery.

Unlike the 16-channel DS21FF44N+, the DS21FT44N+ omits the fourth framer die entirely: pins related to channels 13–16 (e.g., RCLK13/NC, TPOS13/NC, RSIG13/NC) are no-connect (NC), and associated signals like RLOS, RLINK, TLCLK, and TCHCLK are absent-not just unconnected but electrically removed from the MCM design.

Key Specifications

Pinout & Package

DS21FT44N+ uses a 300-pin BGA (27mm × 27mm, 1.27mm pitch) with dedicated power/ground distribution per framer block and shared control resources. The fourth framer quadrant is physically omitted - all pins designated "/NC" (e.g., CS4*/NC, DVDD4/NC, RCLK13/NC) are no-connect and must be left unconnected on PCB layout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS21FT44 and DS21FF44N+, the DS21FT44N+ uniquely balances industrial temperature operation, 12-channel density, and minimized pin count - delivering optimal cost, thermal margin, and layout simplicity for mid-density E1 line cards.

Availability

DS21FT44N+ is available at Aetrix Electronics and suitable for DSLAMs, multiplexers/demultiplexers, and high-density line cards requiring stable component supply, long-term lifecycle support, and industrial-temperature reliability.

Supply support for DS21FT44N+ 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) designs precision analog, mixed-signal, and high-speed communication ICs for demanding infrastructure and industrial applications.

The DS21FT44N+ belongs to Maxim's E1/T1 framer product line, engineered specifically for high-port-density telecom line cards where space, thermal resilience, and standards compliance are critical.

FAQ

What is the maximum number of E1 channels supported by the DS21FT44N+?

The DS21FT44N+ supports exactly 12 independent E1 channels. It integrates three DS21Q44 quad-framer die in a 4×3 multichip module configuration; the fourth framer position is unpopulated, and associated pins (e.g., RCLK13/NC, TPOS13/NC) are no-connect. This is confirmed in the device ordering table and Figure 4-1 (PCB land pattern for 4×3).

Does the DS21FT44N+ support JTAG boundary scan, and how is it implemented?

Yes, the DS21FT44N+ fully supports IEEE 1149.1 JTAG boundary scan. It uses dedicated pins JTCLK, JTDI, JTMS, JTRST*, and JTDOT (JTAG Data Output for 4×3 configuration). JTDOF is marked NC - confirming JTDOT is the active output. This enables structural testing of PCB interconnects and visibility into internal framer register states during manufacturing and field diagnostics.

How does the DS21FT44N+ differ from the DS21FT44 in terms of temperature rating and use cases?

The DS21FT44N+ is rated for –40°C to +85°C, while the DS21FT44 operates from 0°C to +70°C. This extended range makes DS21FT44N+ suitable for uncontrolled environments such as outdoor DSLAM cabinets, central office shelves, and industrial telecom gear. The core functionality, pinout, and electrical specs are otherwise identical - enabling drop-in replacement where thermal margins are insufficient.

Are RLOS, RLINK, and TLCLK signals available on the DS21FT44N+?

No - RLOS, RLINK, RLCLK, RCHCLK, RMSYNC, RFSYNC, TLCLK, TCHCLK, and TCHBLK are explicitly listed as "not available" and "absent" in the DS21FT44/DS21FF44 datasheet (page 2). These signals are deleted from the 4×3 MCM to minimize package size; they are not merely unconnected but electrically omitted from the silicon implementation of DS21FT44N+.

Can the DS21FT44N+ be used as a direct replacement for DS21FT42 in existing designs?

Yes - the DS21FT44N+ is pin compatible with DS21FT42 per the datasheet (Features section), sharing the same 300-pin BGA footprint and signal mapping. However, DS21FT44N+ adds enhanced features including IEEE 1149.1 JTAG, expanded register sets, and improved Sa/Si bit handling. Firmware and layout require no changes, but full benefit requires updating host driver software to leverage new capabilities.