Analog Devices Inc./Maxim Integrated DS21FT44N

Overview

DS21FT44N from Maxim Integrated is a 12-channel E1 framer multichip module (MCM) implementing 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 delivers high-density line-card timing for telecom access equipment with integrated receive/transmit serial data paths, signaling I/O, and system sync interfaces.

For engineers reviewing the DS21FT44N datasheet, DS21FT44N pinout, DS21FT44N application, or DS21FT44N equivalent, this device serves as a temperature-extended industrial-grade alternative to the DS21FT44, enabling deployment in carrier-grade DSLAMs, multiplexers, and high-density line cards where extended thermal stability and E1 channel consolidation are critical.

Technical Context

The DS21FT44N implements a 4×3 MCM architecture-three fully functional DS21Q44 quad-framer die-with all core E1 framing functions retained, including HDLC SA-bit processing, elastic store operation, and per-channel code generation/loopback. Signal reduction includes removal of RFSYNC, RLCLK, RCHCLK, RMSYNC, RLOS, LOTC, TLCLK, TCHCLK, and TCHBLK versus the base DS21Q44 die.

It uses a shared TSYSCLK/RSYSCLK bus across framers and supports both Intel- and Motorola-style parallel bus timing via BTS pin. The JTAG interface (JTCLK, JTDI, JTMS, JTRST, JTDOT) enables boundary-scan testability, while the MUX pin selects between multiplexed and nonmultiplexed bus operation.

Key Specifications

Pinout & Package

DS21FT44N is housed in a 300-pin BGA (27 mm × 27 mm, 1.27 mm pitch) with four distinct framer groups (Framer 1–3 active; Framer 4 NC). Power and ground pins are distributed across multiple locations per framer for low-noise operation. Critical I/O includes RPOS/RNEG, TPOS/TNEG differential pairs per channel, RSER/TSER serial data paths, RSYNC/TSYNC frame sync, and dedicated JTAG signals (JTCLK, JTDI, JTMS, JTRST, JTDOT).

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 12-channel E1 density, extended temperature operation, and drop-in compatibility with existing DS21FT44 layouts-making it optimal for cost-sensitive, thermally demanding line-card upgrades.

Availability

DS21FT44N is available at Aetrix Electronics and suitable for DSLAMs, multiplexers/demultiplexers, and high-density line cards requiring stable component supply across extended temperature ranges and long production lifecycles.

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) is a semiconductor company specializing in precision analog, mixed-signal, and high-reliability interface ICs for communications, industrial, and automotive markets.

The DS21FT44N belongs to Maxim's telecom framer product line, designed specifically for E1/T1 access infrastructure-emphasizing high channel density, JTAG testability, and extended temperature robustness in carrier-class equipment.

FAQ

What is the key functional difference between DS21FT44N and DS21FT44?

The DS21FT44N and DS21FT44 share identical electrical functionality, pinout, and package-but DS21FT44N is qualified for –40°C to +85°C operation, whereas DS21FT44 is rated only from 0°C to +70°C. This makes DS21FT44N suitable for outdoor telecom enclosures and industrial environments where thermal extremes occur. Both use the same 4×3 MCM architecture with 12 active E1 channels.

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

Yes, DS21FT44N fully supports IEEE 1149.1 JTAG boundary scan using dedicated pins: JTCLK, JTDI, JTMS, JTRST*, and JTDOT. Unlike the DS21FF44 (which uses JTDOF), DS21FT44N employs JTDOT as its JTAG data output. This enables comprehensive interconnect testing of all 12 E1 channels' I/O, control bus, and internal logic without requiring physical probe access.

How many E1 channels does DS21FT44N support, and what happens to the fourth framer in the MCM?

DS21FT44N supports exactly 12 E1 channels, implemented across three populated DS21Q44 quad-framer die. The fourth framer position in the 4×3 MCM is unpopulated-meaning all associated signals (e.g., RCLK4, TPOS4, RSIG4, etc.) are designated No Connect (NC) and must be left floating on the PCB. This distinguishes it from the 16-channel DS21FF44N, which populates all four positions.

Can DS21FT44N be used in systems requiring 5 V logic interfacing?

Yes, DS21FT44N features 5 V tolerant inputs and outputs while operating from a 3.3 V digital supply (DVDD). This allows direct connection to 5 V microcontrollers, FPGAs, or legacy peripherals without external level shifters-reducing BOM cost and board space. All control signals (RD*, WR*, CS*, A0–A7, D0–D7) and JTAG pins meet this tolerance specification.

What clock sources does DS21FT44N require for full E1 operation?

DS21FT44N requires two primary clocks: a 2.048 MHz reference clock per E1 channel (applied to RCLKx/TCLKx pins) for data recovery and transmission, and a master reference input CLKSI (typically 8.192 MHz or harmonic) to generate the internal 8.192 MHz 8MCLK. System clocks (SYSCLKx) for each framer are derived internally or supplied externally depending on mode-no separate high-frequency oscillator is needed beyond CLKSI and per-channel E1 clocks.