Analog Devices Inc./Maxim Integrated DS21FT44+

Overview

DS21FT44 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 at 3.3V with 5V-tolerant I/O. It is deployed in high-density line cards for DSLAMs and multiplexers requiring compact, low-power TDM interface aggregation.

For engineers reviewing the DS21FT44 datasheet, DS21FT44 pinout, DS21FT44 application, or DS21FT44 equivalent, key selection criteria include its 12-channel E1 framing capability, 300-pin 27mm × 27mm BGA footprint, JTAG test support, 0°C to +70°C industrial temperature range, and compatibility with DS21FT42 for T1/E1 footprint reuse.

Technical Context

The DS21FT44 implements a 4×3 MCM architecture-three identical DS21Q44 quad-framer dies-with shared control logic and consolidated system clocks (TSYSCLK/RSYSCLK tied). It delivers 12 independent E1 channels via separate receive/transmit data paths (RPOS/RNEG/TPOR/TNEG), frame sync (RSYNC/TSYNC), and signaling interfaces (RSIG/TSIG), all mapped to a unified parallel bus (A0–A7, D0–D7) with Intel/Motorola timing select (BTS).

JTAG boundary-scan (JTCLK/JTDI/JTMS/JTRST/JTDOT) enables board-level testability, while the absence of the fourth framer die eliminates signals like RLOS, RLINK, TLCLK, and TCHCLK-confirmed as NC in the 4×3 configuration. Channel blocking clocks (RCHBLK1–RCHBLK12) and system clock inputs (SYSCLK1–SYSCLK12) are fully retained per active framer.

Key Specifications

Pinout & Package

DS21FT44 uses a 300-pin BGA package (27mm × 27mm, 1.27mm pitch) with four framer groups (1–12), each assigned dedicated receive/transmit data, clock, sync, and signaling pins. The fourth framer die is unpopulated; associated pins (e.g., CS4*, DVDD4, RCLK13–RCLK16, TPOS13–TPOS16) are No Connect (NC). Power and ground are distributed across multiple pins per framer group for noise reduction and current sharing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS21FT42+, DS21FT44 reduces bill-of-materials by integrating clock synthesis; compared with DS21FF44+, it trades 4 channels for lower power and cost while retaining identical packaging and software compatibility - making it optimal for fixed 12-channel deployments.

Availability

DS21FT44 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 verified telecom-grade qualification.

Supply support for DS21FT44 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 ICs for communications, industrial, and automotive markets.

The DS21FT44 belongs to Maxim's TDM framer product line, designed specifically for high-density E1/T1 line interface applications in carrier-class access and aggregation equipment.

FAQ

What is the primary function of the DS21FT44?

The DS21FT44 is a 12-channel E1 framer multichip module that performs full G.704/G.706-compliant E1 framing, including frame alignment, CRC4 generation, Sa/Si bit processing, and HDLC signaling. It integrates three DS21Q44 quad-framer dies in a single 300-pin BGA package and supports JTAG boundary scan for testability. The DS21FT44 handles all physical-layer framing tasks for E1 lines in DSLAMs and multiplexers.

Does the DS21FT44 support both T1 and E1 standards?

The DS21FT44 is specifically designed for E1 (2.048 Mbps) framing and does not support T1 (1.544 Mbps) line rates or framing formats. However, it shares the same 300-pin BGA footprint and register map with the DS21FT42, which is a T1-optimized variant - enabling PCB layout reuse between T1 and E1 designs. The DS21FT44 itself operates exclusively in E1 mode.

How many pins on the DS21FT44 are designated as No Connect (NC)?

The DS21FT44 has 12 explicitly designated NC pins corresponding to the unpopulated fourth framer die: CS4*, DVDD4, DVSS4, RCLK13–RCLK16, RPOS13–RPOS16, RNEG13–RNEG16, RSER13–RSER16, RSIG13–RSIG16, RSYNC13–RSYNC16, SYSCLK13–SYSCLK16, TCLK13–TCLK16, TPOS13–TPOS16, TNEG13–TNEG16, TSER13–TSER16, TSIG13–TSIG16, TSSYNC13–TSSYNC16, TSYNC13–TSYNC16, and RCHBLK13–RCHBLK16. These must remain unconnected per datasheet guidance.

What clock sources does the DS21FT44 require?

The DS21FT44 requires a single external reference clock on the CLKSI pin (typically 8.192 MHz), which it uses to synthesize its internal 8.192 MHz system clock (8MCLK). Each of the 12 E1 channels also requires dedicated receive (RCLK1–RCLK12) and transmit (TCLK1–TCLK12) clocks, plus frame sync signals (RSYNC/TSYNC). No additional crystal or oscillator is needed for core operation due to integrated clock synthesis.

Is the DS21FT44 pin-compatible with any other Maxim framer devices?

Yes, the DS21FT44 is pin-compatible with the DS21FT42 (12-channel T1 framer) - allowing identical PCB footprints for T1 and E1 variants. It is also mechanically compatible with the DS21FF44 (16-channel E1 framer), though DS21FF44 populates all four framer positions and exposes additional signals (e.g., CS4*, RCLK13–RCLK16) that are NC on DS21FT44. Direct substitution without layout change is only valid between DS21FT44 and DS21FT42.