Analog Devices Inc./Maxim Integrated DS2291/87-22291-000

Overview

DS2291/87-22291-000 from Maxim Integrated (now part of Analog Devices) is a T1 line interface IC designed for clock and data recovery from long-loop T1 lines up to 6,000 feet. It integrates Automatic Line Build Out (ALBO), jitter attenuation, B8ZS decoding, bipolar violation detection, and carrier loss monitoring - all operating from a single +5V supply and connecting directly to a 30-pin single in-line header. It serves as the core timing recovery engine in Channel Service Units and T1 test equipment.

For engineers reviewing the DS2291/87-22291-000 datasheet, DS2291/87-22291-000 pinout, DS2291/87-22291-000 application, or DS2291/87-22291-000 equivalent, key selection considerations include its TR 62411-compliant jitter tolerance, ALBO adaptation range (0–6,000 ft), 1.544 MHz recovered clock output, B8ZS enable control, and lock-status indication via the LOCK pin.

Technical Context

The DS2291/87-22291-000 implements analog front-end conditioning with a 1100 Ω input impedance at 772 kHz and –30 to 0 dBSX receiver sensitivity, enabling robust signal acquisition across varying line lengths. Its ALBO circuit dynamically adjusts gain and equalization without external tuning components, while the integrated dejitter circuitry provides frequency-dependent attenuation per TR 62411 Curve A/B up to 100 kHz.

Digital functionality includes a 128-bit recenterable buffer, loopback mux control (LB pin), and real-time status reporting via dedicated open-drain outputs: LOCK (phase/frequency lock), BPV (bipolar violation), RCL (carrier loss), and BL (buffer limit at >120 UIpp jitter). All digital I/Os are TTL-compatible except LCLK/LPOS/LNEG, which require HC-level thresholds.

Key Specifications

Pinout & Package

DS2291/87-22291-000 is housed in a through-hole 30-pin single in-line (SIL) package with 0.100" pin spacing, compatible with standard SIL headers used in CSUs and test fixtures. Pin 1 (VDD) is marked by a notch on the package body.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS2290 and DS2180A, the DS2291/87-22291-000 uniquely combines adaptive line build-out, TR 62411-compliant jitter attenuation, and B8ZS-aware signal recovery in a single 30-pin SIL package - making it irreplaceable for long-loop T1 monitoring and CSU applications where signal integrity and autonomous adaptation are critical.

Availability

DS2291/87-22291-000 is available at Aetrix Electronics and suitable for Channel Service Units, T1 test equipment, and network monitoring systems requiring stable component supply, long-term lifecycle support, and traceable sourcing for telecom infrastructure programs.

Supply support for DS2291/87-22291-000 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 power management ICs for communications, industrial, and computing applications.

The DS2291/87-22291-000 belongs to Maxim's T1/E1 interface product line, engineered specifically for carrier-grade line interface units requiring autonomous signal recovery, jitter mitigation, and standards-compliant diagnostics in unconditioned loop environments.

FAQ

What is the primary function of the DS2291/87-22291-000 in a T1 system?

The DS2291/87-22291-000 functions as a T1 line interface IC that recovers clock and bipolar data from long-loop T1 lines up to 6,000 feet. It performs automatic line build out (ALBO), jitter attenuation per TR 62411, B8ZS decoding, bipolar violation detection, and carrier loss monitoring - all within a single +5V-powered 30-pin SIL package. The DS2291/87-22291-000 delivers synchronized RCLK, RPOS, and RNEG outputs essential for downstream frame synchronization and error analysis.

How does the ALBO circuit in the DS2291/87-22291-000 adapt to different T1 line lengths?

The DS2291/87-22291-000 ALBO circuit dynamically adjusts gain and equalization in real time to compensate for signal loss across T1 line lengths from 0 to 6,000 feet - without requiring external tuning components or manual calibration. This adaptation ensures consistent receiver sensitivity (–30 to 0 dBSX) and reliable lock acquisition regardless of line impedance or distance. The DS2291/87-22291-000 achieves this using internal feedback loops that monitor signal integrity and adjust analog front-end parameters autonomously.

What does the LOCK pin indicate, and how is it used in system design?

On the DS2291/87-22291-000, the LOCK pin is an active-high open-drain output that signals successful phase-and-frequency lock to the incoming T1 signal. When high, it confirms stable 1.544 MHz clock recovery and valid data alignment at RPOS/RNEG. System designers use this pin for hardware-level status monitoring, fault detection, and automatic failover - for example, disabling downstream processing until LOCK asserts. The DS2291/87-22291-000 guarantees LOCK assertion only after meeting TR 62411 jitter tolerance criteria.

Can the DS2291/87-22291-000 handle B8ZS-encoded T1 signals, and how is it configured?

Yes, the DS2291/87-22291-000 supports B8ZS-encoded T1 signals via the B8ZS pin (Pin 20). When tied high, it decodes B8ZS code words and replaces them with eight consecutive zeros; when tied low or left open, it passes raw bipolar data without modification. Bipolar violations (BPV) are reported independently via the BPV pin, though BPV detection is disabled during B8ZS decoding. This configuration allows the DS2291/87-22291-000 to interoperate with both legacy AMI and modern B8ZS-framed T1 networks.

What is the purpose of the DJA pin, and what happens when it is asserted high?

The DJA (Disable Jitter Attenuation) pin on the DS2291/87-22291-000 controls activation of the integrated dejitter circuitry. When DJA is tied low (default), the DS2291/87-22291-000 applies TR 62411-compliant attenuation across 100 Hz–100 kHz. When DJA is tied high, jitter attenuation is fully bypassed - passing all input jitter directly to RCLK, RPOS, and RNEG. This mode is used only when downstream circuitry handles jitter cleanup, but the DS2291/87-22291-000 datasheet recommends keeping DJA low for most T1 transmission applications.