Analog Devices Inc./Maxim Integrated 78P2351R-IM/F

Overview

The 78P2351R-IM/F from Teridian Semiconductor is a second-generation Line Interface Unit (LIU) for 155.52 Mbit/s STM-1e electrical SDH interfaces, integrating clock and data recovery (CDR) in both transmit and receive paths to perform NRZ-to-CMI conversion. It supports ITU-T G.703-compliant coaxial transmission over 75Ω cable, handles >12.7 dB cable loss, and operates from a single 3.3 V supply in industrial temperature range (–40°C to +85°C).

For engineers reviewing the 78P2351R-IM/F datasheet, 78P2351R-IM/F pinout, 78P2351R-IM/F application, or 78P2351R-IM/F equivalent, this device serves as a compact, low-jitter solution for SFP transceivers requiring plesiochronous/synchronous timing modes, adaptive equalization, LVPECL-compatible system interfacing, and configurable serial or hardware control.

Technical Context

The 78P2351R-IM/F implements dual-path CDR using Delay Locked Loops (DLLs): one in the receiver for jitter-tolerant recovery of CMI-encoded 155.52 Mbps signals, and another in the transmitter for NRZ-to-CMI encoding with optional FIFO-based re-timing. Its adaptive equalizer compensates for inter-symbol interference from long coax runs, while the fixed backplane equalizer supports up to 1.5 m FR4 trace compensation.

Configuration is supported via either hardware control pins (e.g., CKSL, SPSL, TXPD) or a 4-wire serial interface (SEN/SCK_MON/SDI/SDO) operating up to 20 MHz. The device supports three transmit timing modes-synchronous (FIFO-enabled), plesiochronous (FIFO-bypassed), and loop-timing-and includes Rx LOS detection, monitor mode (+20 dB flat gain), and local/remote analog/digital loopback functions.

Key Specifications

Pinout & Package

Package: 7×7 mm, 56-pin QFN (MLF) with exposed thermal pad - optimized for space-constrained SFP modules and high-density line cards.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Line Interface Unit applications.

Compared with MAX3675 and DS38EP100, the 78P2351R-IM/F uniquely integrates full G.703-compliant CMI encoding/decoding, adaptive equalization for >12.7 dB loss, and receiver monitor mode - making it the only drop-in solution for standards-compliant STM-1e SFP and line card designs without external logic or tuning.

Availability

The 78P2351R-IM/F is available at Aetrix Electronics and suitable for STM-1e SFP modules, SDH/ATM line cards, and digital microwave radio interfaces requiring stable component supply, long-term lifecycle assurance, and traceable sourcing for carrier-grade deployments.

Supply support for 78P2351R-IM/F 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

Teridian Semiconductor was a fabless analog/mixed-signal IC company specializing in precision metrology and telecommunications interface solutions before its acquisition by Maxim Integrated in 2010.

The 78P2351R-IM/F belongs to Teridian's Line Interface Unit product line, engineered specifically for carrier-class SDH/SONET electrical physical layer interfaces requiring low-jitter CDR, coax driver/receiver integration, and standards-compliant NRZ-to-CMI conversion.

FAQ

What is the primary function of the 78P2351R-IM/F in an STM-1e system?

The 78P2351R-IM/F serves as a complete Line Interface Unit that converts NRZ-encoded data from framer/mapper ICs into CMI-encoded signals for 75Ω coaxial transmission at 155.52 Mbps, while simultaneously recovering clock and data from incoming CMI signals. It integrates dual CDRs, adaptive equalization, and configurable timing modes to meet ITU-T G.703 and GR-253-CORE requirements without external components.

Does the 78P2351R-IM/F support both synchronous and plesiochronous clocking modes?

Yes, the 78P2351R-IM/F supports three transmit timing modes: synchronous (with FIFO re-timing), plesiochronous (FIFO bypassed, clock recovered from data), and loop-timing (using recovered receive clock). These modes are selected via SMOD[1:0] bits in the Mode Control Register or corresponding hardware pins (CKMODE), enabling deployment across diverse SDH infrastructure where reference clock availability varies.

How does the adaptive equalizer in the 78P2351R-IM/F improve system margin?

The adaptive equalizer in the 78P2351R-IM/F dynamically compensates for inter-symbol interference caused by frequency-dependent attenuation in long coaxial cables, enabling reliable operation with >12.7 dB of cable loss. This eliminates the need for manual tuning or external equalizer ICs, directly improving bit-error-rate (BER) margin in real-world installations where cable length and quality vary.

Can the 78P2351R-IM/F be configured without a microcontroller?

Yes, the 78P2351R-IM/F supports hardware-only configuration using dedicated control pins (e.g., CKSL, SPSL, TXPD, LPBK) for basic functions including reference clock selection, power-down, and analog loopback. In pin-control mode (SPSL low), unused serial interface pins (SDI, SDO, SEN) are tied to fixed logic levels, allowing full operation without firmware or serial bus infrastructure.

What is the purpose of the Rx Monitor Mode in the 78P2351R-IM/F?

Rx Monitor Mode in the 78P2351R-IM/F applies +20 dB of flat gain before the adaptive equalizer stage, enabling reliable signal acquisition from monitoring taps with up to 6 dB of coax loss. During this mode, Rx LOS detection is disabled to prevent false alarms, making it ideal for non-intrusive diagnostics and in-service testing in live SDH networks.