Analog Devices Inc./Maxim Integrated DS26521L+

Overview

DS26521L+ from Maxim Integrated is a single-channel T1/E1/J1 framer and line interface unit (LIU) IC supporting long-haul and short-haul operation, configurable for D4/SLC-96/ESF (T1), G.704/CRC-4 (E1), and J1 framing, with internal software-selectable 100Ω/110Ω/120Ω/75Ω termination and crystal-less jitter attenuator compliant with ITU-T G.736/G.742/G.823 and ETSI CTR 12/13 - deployed in CSUs, DSUs, and T1/E1 test equipment.

For engineers reviewing the DS26521L+ datasheet, DS26521L+ pinout, DS26521L+ application, or DS26521L+ equivalent, key selection criteria include T1/E1/J1 framing flexibility, integrated LIU+framer functionality, dual-interface control (8-bit parallel or SPI), receive signal level indication range (–2.5dB to –44dB in E1 mode), and RoHS-compliant 64-pin LQFP packaging.

Technical Context

The DS26521L+ integrates a full-duplex T1/E1/J1 transceiver with independent framer and LIU blocks, enabling simultaneous framing, signaling extraction/insertion, and physical-layer line driving/receiving. It supports host-mode clock adaptation of external master clocks (1.544MHz or 2.048MHz) and includes elastic stores for H.100 (CT Bus) backplane compatibility.

Jitter attenuation is implemented via a crystal-less architecture meeting ETSI and ITU-T standards, while alarm detection (LOS per G.775/ETS 300 233/T1.231) and transmit open/short-circuit diagnostics are embedded at the LIU level. Configuration occurs through either an 8-bit parallel port or SPI interface, with register-level access to all framer, LIU, and BERT functions.

Key Specifications

Pinout & Package

DS26521L+ is housed in a 64-pin LQFP package (56-G4019-001), thermally enhanced for sustained T1/E1 line drive operation. Pin assignments follow Maxim's standardized T1/E1 transceiver layout with dedicated TDM backplane interface (IBO), system clock inputs (CLKIN, RSYNC, TSSYNCIO), and microprocessor control signals (RD, WR, CS, D0–D7).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar T1/E1 framer+LIU applications.

Compared with DS2155LN+ and MAX3005EUP+, the DS26521L+ uniquely combines framer, LIU, jitter attenuator, and dual-interface control in one device - delivering lowest component count and highest integration for single-channel T1/E1 edge equipment.

Availability

DS26521L+ is available at Aetrix Electronics and suitable for channel service units (CSUs), data service units (DSUs), and T1/E1 test equipment requiring stable component supply, long-term lifecycle assurance, and traceable sourcing for telecom infrastructure programs.

Supply support for DS26521L+ 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 power management ICs for communications, industrial, and computing markets.

The DS26521L+ belongs to Maxim's T1/E1/J1 transceiver product line, engineered specifically for carrier-class and enterprise-grade digital access equipment requiring standards-compliant, low-power, single-chip framer+LIU integration.

FAQ

What is the primary function of the DS26521L+ in a T1/E1 system?

The DS26521L+ serves as a fully integrated single-channel T1/E1/J1 framer and line interface unit (LIU), performing physical-layer line driving/receiving, framing (D4/ESF/G.704/CRC-4), signaling extraction/insertion, and jitter attenuation. It replaces discrete framer and LIU ICs in CSUs, DSUs, and test equipment - enabling compact, standards-compliant digital access designs without external clock synthesis or line driver components.

Does the DS26521L+ support both T1 and E1 framing simultaneously?

No, the DS26521L+ operates in a single mode per configuration: T1 (1.544MHz), E1 (2.048MHz), or J1. Mode selection is determined at initialization via register settings and master clock frequency. While it cannot process both T1 and E1 frames concurrently, its software-selectable termination and framing registers allow field-reconfigurable deployment across all three standards using the same DS26521L+ hardware.

What clock sources does the DS26521L+ accept, and how are they used?

The DS26521L+ accepts an external master clock at 1.544MHz (T1/J1) or 2.048MHz (E1) on the CLKIN pin. Internally, this clock is adapted for framer timing, LIU line rate generation, and jitter attenuator reference. The device also supports H.100 CT Bus synchronization via RSYNC and TSSYNCIO pins - enabling precise timing alignment in backplane-based TDM switch fabrics without requiring additional clock distribution ICs.

How does the DS26521L+ handle line fault detection and alarm generation?

The DS26521L+ implements comprehensive line monitoring including Loss of Signal (LOS) per G.775, ETSI 300 233, and T1.231; receive signal level indication (–2.5dB to –44dB in E1 mode); and transmit open/short-circuit detection. Alarms such as AIS, RAI, and LOF are automatically detected and can be inserted into outgoing frames - providing full compliance with telecom operations support systems (OSS) requirements for remote fault isolation and network management.

Is the DS26521L+ pin-compatible with earlier revisions like DS26521LN?

Yes, the DS26521L+ is a lead-free/RoHS-compliant version of the DS26521LN and shares identical pinout, package (64-pin LQFP), electrical specifications, and register map. The "+" suffix denotes environmental compliance only - no functional or timing differences exist between DS26521LN and DS26521L+, making it a direct drop-in replacement in existing designs requiring RoHS adherence.