Analog Devices Inc./Maxim Integrated DS21Q348

Overview

DS21Q348 from Maxim Integrated is a quad-channel 3.3V E1/T1/J1 line interface unit (LIU) supporting long-haul and short-haul trunks, with internal software-selectable 75Ω/100Ω/120Ω receive termination, crystal-less jitter attenuation (32-bit or 128-bit FIFO), and AMI/HDB3/B8ZS encoding/decoding. It operates across 0°C to +70°C in a 144-ball CSBGA package and targets telecom access equipment requiring multi-line synchronization and line build-out compliance.

For engineers reviewing the DS21Q348 datasheet, DS21Q348 pinout, DS21Q348 application, or DS21Q348 equivalent, key selection considerations include its quad-channel integration, G.703/G.704-compliant analog interface, programmable line build-out for E1 (0dB to –22.5dB) and T1 (CSU/DSX-1), 2.048MHz/1.544MHz master clock flexibility, and hardware/serial/parallel control port options.

Technical Context

The DS21Q348 implements four independent LIU channels sharing a common 3.3V supply and control infrastructure, each featuring fully integrated clock/data recovery, bipolar-to-NRZ conversion, and transformer-coupled analog I/O (RTIP/RRING, TTIP/TRING). Its jitter attenuator is configurable in either transmit or receive path with selectable 32-bit or 128-bit depth, synchronized to recovered RCLK.

Each channel supports independent E1 or T1 mode selection (ETS bit), programmable receive sensitivity (–43dBm for E1, –36dBm for T1), and line build-out generation per ITU G.703 and ANSI T1.403-1999 - including CSU (0dB, –7.5dB, –15dB, –22.5dB) and DSX-1 profiles - with automatic equalization and carrier loss detection per G.775.

Key Specifications

Pinout & Package

DS21Q348 uses a 144-ball CSBGA (17mm × 17mm) package with 0.8mm ball pitch, optimized for thermal dissipation in multi-channel line cards. Pin assignments are defined in Section 8 of the datasheet (Table 8-1) and support three interface modes: parallel (muxed/nonmuxed Intel/Motorola), serial (SPI-like), and hardware control.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar line interface unit applications.

Compared with DS21348GN+ and DS2155, DS21Q348 delivers higher channel density, eliminates crystal dependency, and provides full CSU/DSX-1 line build-out - making it optimal for new multi-line telecom infrastructure where board area, thermal management, and standards compliance are prioritized.

Availability

DS21Q348 is available at Aetrix Electronics and suitable for DSLAM line cards, enterprise TDM gateways, mobile backhaul nodes, and industrial SCADA multiplexers requiring stable component supply across multi-year production cycles.

Supply support for DS21Q348 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 power management ICs for communications, industrial, and computing markets.

The DS21Q348 belongs to Maxim's telecom line interface product line, designed specifically for E1/T1/J1 physical layer interfacing in carrier-class access equipment and enterprise infrastructure with emphasis on jitter performance, standards compliance, and multi-channel integration.

FAQ

What is the primary function of the DS21Q348 in a telecom system?

The DS21Q348 serves as a quad-channel E1/T1/J1 line interface unit (LIU), performing clock/data recovery, bipolar-to-NRZ conversion, line build-out generation, and protocol encoding/decoding (AMI/HDB3/B8ZS). In telecom systems, DS21Q348 bridges digital backplanes to analog copper trunks while ensuring G.703/G.704 compliance and jitter attenuation - critical for maintaining signal integrity across long-haul and short-haul links.

Does the DS21Q348 require an external crystal for jitter attenuation?

No, the DS21Q348 features a crystal-less jitter attenuator that operates using only the 2.048MHz (or optional 1.544MHz for T1) master clock applied to the MCLK pin. This eliminates the need for an external crystal oscillator, reducing bill-of-materials cost and PCB layout complexity while still meeting ITU G.823 jitter tolerance requirements. The DS21Q348 jitter attenuator is configurable to 32-bit or 128-bit depth and can be placed in either the transmit or receive data path.

How does the DS21Q348 handle different line impedances like 75Ω, 100Ω, and 120Ω?

The DS21Q348 supports internal software-selectable receive-side termination for 75Ω, 100Ω, and 120Ω applications via control register CCR5. This eliminates the need for external termination resistors or jumpers, simplifying design and enabling runtime reconfiguration. The termination is applied at the RTIP/RRING analog inputs and adapts automatically to incoming signal levels - supporting both short-haul and long-haul trunks without hardware changes. DS21Q348 maintains specified receive sensitivity (–43dBm for E1, –36dBm for T1) across all three impedance modes.

What control interface options does the DS21Q348 support?

The DS21Q348 supports three distinct control interface modes selected via BIS0 and BIS1 pins: parallel (muxed or nonmuxed Intel/Motorola bus), serial (SPI-compatible 3-wire), and hardware mode (dedicated logic pins for loopback, alarm, and mode control). Each mode maps differently to shared pins - for example, in hardware mode, pins like L0–L2 and CES directly configure loopback and encode settings without register writes. This flexibility allows DS21Q348 to integrate with microcontrollers, FPGAs, or fixed-function logic depending on system architecture requirements.

Can the DS21Q348 generate and detect in-band loop codes for remote diagnostics?

Yes, the DS21Q348 can generate and detect in-band loop codes from 1 to 16 bits, including CSU-specific loop-down codes, as defined in ANSI T1.403 and ITU G.704. Loop code length is programmable via registers CCR3 (transmit) and CCR4 (receive), and detection status is reported in status registers. This capability enables standardized remote loopback testing across E1/T1 networks - allowing network operators to verify end-to-end connectivity and isolate faults without dispatching field technicians. DS21Q348 also supports local, analog, and dual loopbacks for comprehensive diagnostics.