Analog Devices Inc./Maxim Integrated DS21448G+

Overview

DS21448G+ from Maxim Integrated is a quad-port E1/T1/J1 line interface unit (LIU) designed for short- and long-haul telecom trunk interfaces. It integrates four independent transceivers, supports 75Ω/120Ω line impedances, delivers programmable line build-outs (0dB to –22.5dB), and operates from a single 3.3V supply. It serves in multiservice access platforms and T1/E1 cross-connects requiring precise G.703/G.704 compliance.

For engineers reviewing the DS21448G+ datasheet, DS21448G+ pinout, DS21448G+ application, or DS21448G+ equivalent, key selection criteria include quad-channel E1/T1 line build-out programmability, crystal-less jitter attenuation with 2.048MHz/1.544MHz master clock support, AMI/HDB3/B8ZS encoding/decoding, and IEEE 1149.1 JTAG boundary scan test capability.

Technical Context

The DS21448G+ implements four fully independent LIU channels, each with integrated transmit drivers, receive amplifiers, clock/data recovery, and digital signal processing. Each channel supports selectable E1 (2.048Mbps) or T1 (1.544Mbps) framing, internal software-configurable 75Ω/100Ω/120Ω receive termination, and NRZ/bipolar data I/O.

Its jitter attenuator uses a 32-bit or 128-bit PLL architecture synchronized to MCLK, synthesizing backplane clocks (2.048–16.384MHz) from recovered timing. The device includes hardware-mode configuration pins (BIS0/BIS1/PBTS), parallel (Intel/Motorola) or serial control interface, and full diagnostic features including PRBS generation/detection, loopbacks (local/remote/analog/dual), and in-band loop-code handling (1–16 bits).

Key Specifications

Pinout & Package

DS21448G+ is supplied in a lead-free, RoHS-compliant 144-ball TE-PBGA package (56-G6020-001), 12mm × 12mm, 0.8mm ball pitch, with exposed thermal pad. Pin assignments are identical to DS21448 (non-"+") variant; "+" denotes RoHS compliance only.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad E1/T1 line interface applications.

Compared with DS21Q348, DS21448G+ adds IEEE 1149.1 JTAG for production test and field diagnostics; compared with MC2021, it provides unified E1/T1/J1 support, crystal-less jitter attenuation, and software-selectable line build-outs-making DS21448G+ the only option meeting full ITU/ANSI multi-standard compliance in a single RoHS-compliant package.

Availability

DS21448G+ is available at Aetrix Electronics and suitable for integrated multiservice access platforms, T1/E1 cross-connects, and wireless base station backhaul requiring stable component supply, long lifecycle support, and RoHS-compliant manufacturing.

Supply support for DS21448G+ 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and RF ICs for communications, computing, and industrial markets.

The DS21448G+ belongs to Maxim's telecom line interface product line, engineered specifically for carrier-grade TDM infrastructure requiring multi-standard E1/T1/J1 interoperability, low-jitter clock recovery, and production-ready testability.

FAQ

What is the primary function of the DS21448G+ in telecom systems?

The DS21448G+ functions as a quad-port E1/T1/J1 line interface unit (LIU), providing complete physical layer interfacing-including clock/data recovery, line build-out generation, AMI/HDB3/B8ZS encoding/decoding, and alarm detection-for four independent TDM trunks. Its role in telecom systems is to bridge digital backplanes to legacy copper infrastructure while maintaining strict ITU and ANSI compliance. DS21448G+ replaces discrete transceiver solutions with a single, highly integrated IC that reduces board space and improves timing accuracy.

Does the DS21448G+ require an external crystal oscillator?

No, the DS21448G+ does not require an external crystal oscillator. It implements a crystal-less jitter attenuator using a 32-bit or 128-bit PLL architecture that locks to either a 2.048MHz master clock (for E1) or an optional 1.544MHz clock (for T1). This eliminates crystal placement, associated layout constraints, and frequency tolerance dependencies-reducing bill-of-materials count and improving reliability. DS21448G+ relies solely on the MCLK input for all timing functions, including backplane clock synthesis.

How does the DS21448G+ handle line impedance matching for E1 and T1 applications?

The DS21448G+ supports software-selectable receive-side termination for 75Ω, 100Ω, and 120Ω line impedances via register-controlled internal termination resistors-eliminating external resistor networks. For transmit, it generates G.703-compliant E1 waveshapes for 75Ω or 120Ω loads and DSX-1/CSU line build-outs (0dB, –7.5dB, –15dB, –22.5dB) for T1. DS21448G+ achieves this through integrated current-mode drivers and programmable output stages, enabling deployment across diverse cable plant configurations without hardware changes.

What diagnostic capabilities does the DS21448G+ provide for field maintenance?

The DS21448G+ includes comprehensive on-chip diagnostics: PRBS pattern generation/detection (2¹⁵–1 for E1, QRSS for T1), four loopback modes (local, remote, analog, dual), in-band loop-code generation/detection (1–16 bits), real-time error counting (BPV/CV/EXZ), and AIS/RCL alarm reporting. These features allow full link validation and fault isolation without external test gear. DS21448G+ also supports IEEE 1149.1 JTAG boundary scan for interconnect testing and in-system debug-critical for high-availability telecom equipment maintenance.

Is the DS21448G+ pin-compatible with other members of the DS21448 family?

Yes, DS21448G+ is pin-compatible with all DS21448 variants in the 144-ball TE-PBGA package-including DS21448, DS21448N, and DS21448N+. The "+" suffix indicates lead-free/RoHS-compliant packaging only; electrical characteristics, pinout, register map, and functional behavior are identical across these variants. This allows drop-in replacement during manufacturing transitions or environmental compliance upgrades without PCB redesign. DS21448G+ maintains full backward compatibility with existing DS21448-based designs.