Analog Devices Inc./Maxim Integrated DS21FF42

Overview

DS21FF42 from Maxim Integrated is a 16-channel T1 framer multichip module (MCM) implementing four DS21Q42 quad-framer die in a single 300-pin, 27mm × 27mm, 1.27mm-pitch BGA package. It operates at 3.3V with 5V-tolerant I/O, supports IEEE 1149.1 JTAG boundary scan, and delivers full T1 framing functionality for high-density line cards in DSLAMs and multiplexers.

For engineers reviewing the DS21FF42 datasheet, DS21FF42 pinout, DS21FF42 application, or DS21FF42 equivalent, this device enables scalable T1 channel density with minimal footprint and power-critical when optimizing T3 backplane aggregation using mixed DS21FF42/DS21FT42 configurations.

Technical Context

The DS21FF42 integrates four independent DS21Q42 T1 framer die into one MCM, each supporting full T1 framing, HDLC control, FDL/FS extraction/insertion, and per-channel code generation/detection. All 16 channels retain complete receive/transmit signal paths-including RPOS/RNEG, TPOS/TNEG, RSYNC/TSYNC, and dedicated clock inputs (RCLK/TCLK/TSYSCLK).

Unlike the base DS21Q42, the MCM consolidates TSYSCLK/RSYSCLK and omits RFSYNC, RLCLK, RCHCLK, RMSYNC, RLOS, LOTC, TLCLK, TCHCLK, and TCHBLK signals. Channel blocking clocks (RCHBLK1–RCHBLK16) and JTAG (JTCLK/JTDI/JTMS/JTRST/INT*) are fully retained for system-level timing control and testability.

Key Specifications

Pinout & Package

DS21FF42 uses a 300-pin, 27mm × 27mm, 1.27mm-pitch BGA package. Pin assignments follow the standardized DS21FF42 (4×4) PCB land pattern (Figure 3-1), with dedicated I/O groups per framer quadrant and shared control signals (JTAG, INT*, CS*, RD*/WR*, address/data bus).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar T1 framer applications.

Compared with DS21FF44, DS21FF42 provides native T1 framing and timing without translation layers; compared with DS21Q42, it cuts inter-die routing, power, and assembly cost by consolidating four devices-but requires MCM-level thermal management and BGA rework capability.

Availability

DS21FF42 is available at Aetrix Electronics and suitable for DSLAM line cards, T1 multiplexers, and carrier-class access nodes requiring stable component supply, long-term lifecycle support, and traceable sourcing for telecom infrastructure programs.

Supply support for DS21FF42 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 solutions for communications, industrial, and automotive markets.

The DS21FF42 belongs to Maxim's T1/E1 framer product line, designed specifically for high-channel-density telecom infrastructure where space, power, and signal integrity are constrained-targeting DSLAMs, optical muxes, and carrier-grade access equipment.

FAQ

What is the primary function of the DS21FF42 in a T1 line card?

The DS21FF42 serves as a 16-channel T1 framer, performing frame synchronization, CRC validation, DS0 channel extraction, and alarm detection (e.g., LOS, AIS) for each T1 line. It replaces four discrete DS21Q42 quad-framers, integrating all functions-including HDLC control, FDL/FS handling, and JTAG test-into a single 300-pin BGA package. Its design directly targets high-density DSLAM and multiplexer line cards where board space and power efficiency are critical.

Does the DS21FF42 support both T1 and E1 standards?

The DS21FF42 is specifically designed for T1 (1.544 Mbps) framing and does not natively support E1 (2.048 Mbps) standards. However, its pin-compatible counterpart DS21FF44 provides identical 16-channel architecture optimized for E1. Both share the same 27mm × 27mm BGA footprint and control interface, enabling hardware reuse across T1 and E1 deployments-only firmware, clock source, and framing configuration differ between DS21FF42 and DS21FF44.

How does the DS21FF42 handle clocking for 16 independent T1 channels?

The DS21FF42 provides dedicated clock inputs for each channel: RCLK1–RCLK16 for receive timing and TCLK1–TCLK16 for transmit timing. It also includes per-channel RCHBLK outputs for receive channel blocking control and supports system-level TSYSCLK/RSYSCLK (tied together internally). This architecture allows fully asynchronous operation across all 16 T1 lines-essential for aggregating diverse, independently timed T1 feeds in DSLAM backplanes without introducing jitter or phase misalignment.

What JTAG capabilities does the DS21FF42 provide?

The DS21FF42 implements full IEEE 1149.1 JTAG boundary scan with dedicated JTCLK, JTDI, JTMS, JTRST*, and JTDO pins. It supports device identification, interconnect testing, and in-system programming of internal registers. Unlike basic scan chains, the DS21FF42's JTAG interface is integrated with its framer control logic-enabling real-time visibility into framing status, alarm conditions, and channel-level error counters without halting normal operation.

Is the DS21FF42 suitable for industrial temperature applications?

The standard DS21FF42 is rated for 0°C to +70°C operation and is intended for commercial-grade telecom infrastructure such as central office DSLAMs and carrier-class access nodes. For extended temperature range (-40°C to +85°C), the DS21FF42N variant is available-identical in functionality and pinout but qualified for harsher environments like outdoor cabinets or uncontrolled telco shelters. The DS21FF42 itself is not specified for industrial temperature use.