Analog Devices Inc./Maxim Integrated DS21Q41BT

Overview

DS21Q41BT from Maxim Integrated (now part of Analog Devices) is a quad T1 framing transceiver IC designed for telecom line cards and digital access equipment. It integrates four independent DS1/ISDN-PRI framers supporting D4, ESF, and SLC-96 formats; provides 8-bit parallel control port with Intel/Motorola bus timing; features dual two-frame elastic stores per framer up to 8.192 MHz; and operates from a single 5V supply in industrial temperature range (−40°C to +85°C).

For engineers reviewing the DS21Q41BT datasheet, DS21Q41BT pinout, DS21Q41BT application, or DS21Q41BT equivalent, this page delivers verified technical context, exact pin functions per framer, real-world timing roles (e.g., TCLK0 at 1.544 MHz, RCHCLK at 192 kHz), confirmed ANSI/ITU compliance (T1.403, G.704), and validated alternatives for multi-T1 framer replacement in carrier-grade systems.

Technical Context

The DS21Q41BT implements four fully autonomous T1 framers on a monolithic die-each with independent transmit/receive paths, dedicated elastic stores, and separate frame synchronization. Each framer supports robbed-bit signaling extraction/insertion, BPV/LCV/EXZ/CRC6 error counting, and programmable output clocks for Fractional T1 and ISDN-PRI loopback.

Its control architecture uses two framer-select lines (FS0/FS1) to multiplex access across four identical register sets (addresses 20h–7Fh), enabling reuse of DS2141A firmware with minimal modification. The device supports both multiplexed and non-multiplexed 8-bit parallel buses, configurable via MUX and BTS pins, and includes hardware-level loopback modes (payload and framer) for system validation.

Key Specifications

Pinout & Package

DS21Q41BT is housed in a 128-pin TQFP (Thin Quad Flat Package) with 0.4 mm pitch, optimized for high-density telecom PCB layouts and thermal dissipation in line-card applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS21Q43 and DS2155, DS21Q41BT uniquely delivers quad T1 functionality in one package with native D4/ESF/SLC-96 support, eliminating inter-device skew and reducing PCB routing complexity - critical for high-density line cards requiring deterministic timing and minimal component count.

Availability

DS21Q41BT is available at Aetrix Electronics and suitable for DSLAM line cards, TDM-over-IP gateways, ISDN-PRI access servers, central office channel banks, and telecom test equipment requiring stable component supply and long-term lifecycle assurance.

Supply support for DS21Q41BT 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 (acquired by Analog Devices in 2021) is a semiconductor company specializing in precision analog, mixed-signal, and high-reliability ICs for communications, industrial, and automotive markets.

The DS21Q41BT belongs to Maxim's telecom line interface portfolio, engineered specifically for carrier-class T1/E1 infrastructure where framing accuracy, jitter tolerance, and standards compliance are non-negotiable design requirements.

FAQ

What is the operating voltage range for DS21Q41BT?

The DS21Q41BT operates from a single 5.0 V ±0.5 V supply, making it compatible with standard 5V logic families and legacy telecom power architectures. This voltage powers both core logic and I/O buffers, with four VDD pins (pins 15, 47, 79, 111) and four VSS pins (14, 46, 78, 110) distributed for low-noise decoupling. Operation outside this range may cause functional failure or permanent damage to DS21Q41BT.

Does DS21Q41BT support both D4 and ESF framing modes?

Yes, DS21Q41BT supports D4, ESF, and SLC-96 framing formats on all four framers independently. Framing mode is configured per framer via CCR2 bits TFM (transmit) and RFM (receive); ESF mode enables CRC6 calculation, FDL insertion/extraction, and multiframe alignment. DS21Q41BT meets ANSI T1.403 and ITU G.704 requirements in both modes - a key capability distinguishing it from single-mode alternatives.

How many pins does DS21Q41BT have, and what is its package type?

DS21Q41BT is packaged in a 128-pin TQFP (Thin Quad Flat Package) with 0.4 mm lead pitch. The pinout is fully documented across Tables 1-1 through 1-3 in the official datasheet, including 16 dedicated framer I/O pins per channel (e.g., TCLK0–TCLK3, RCLK0–RCLK3), 8-bit parallel control bus signals (D0–D7, A0–A6, CS, RD, WR), and global functions like INT and TEST. This package balances thermal performance, routing density, and manufacturability for telecom line cards.

Can DS21Q41BT perform per-channel loopback?

Yes, DS21Q41BT supports per-channel loopback through multiple mechanisms: framer loopback (FLB) forces unframed all-ones transmission on selected framer outputs, while payload loopback (PLB) routes corrected 192-bit payload from receive to transmit path - both configurable per framer via CCR1 bits FLB and PLB. Additionally, TCHBLK and RCHBLK outputs allow software-controlled per-channel blocking for diagnostic isolation - a capability confirmed in DS21Q41BT's functional description and register map.

Is DS21Q41BT pin-compatible with any other Maxim quad framers?

Yes, DS21Q41BT is explicitly stated as pin-compatible with DS21Q43, the quad E1 framer. Both share identical 128-pin TQFP footprints and parallel control port pin assignments (e.g., FS0/FS1, CS, RD/WR, D0–D7). However, DS21Q41BT implements T1-specific features (D4 framing, 1.544 MHz clocks, robbed-bit signaling) not present in DS21Q43, so electrical and functional compatibility is limited to mechanical and bus-interface levels - not drop-in replacement in T1 systems.