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

Overview

The 78P2351R-IMR/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 75Ω coaxial transmission, handles >12.7 dB cable loss, operates from a single 3.3 V supply, and is packaged in a 7×7 mm 56-pin QFN for SFP module integration.

For engineers reviewing the 78P2351R-IMR/F datasheet, 78P2351R-IMR/F pinout, 78P2351R-IMR/F application, or 78P2351R-IMR/F equivalent, this device serves as a complete LIU solution requiring only a reference clock and wideband transformer - with configurable HW/SW control, adaptive equalization, LVPECL-compatible NRZ I/O, and compliance to ITU-T G.703, G.813, G.825, G.958, and Telcordia GR-253-CORE jitter standards.

Technical Context

The 78P2351R-IMR/F implements dual-path CDR using Delay Locked Loops (DLLs): one in the receiver for recovering clock/data from transformer-coupled CMI signals, and another in the transmitter for re-timing NRZ inputs before CMI encoding. Its adaptive equalizer compensates for inter-symbol interference across >12.7 dB of coaxial cable loss, while the optional fixed backplane equalizer supports up to 1.5 m of FR4 trace.

Transmit operation supports three timing modes - synchronous (with ±4-bit FIFO), plesiochronous (FIFO bypassed), and loop-timing (recovered Rx clock drives Tx DLL) - selectable via hardware pins or serial register control. The device also provides Rx Monitor Mode (20 dB flat gain), Loss of Signal detection, analog/digital loopback, and programmable pulse amplitude boost (5% or 10%).

Key Specifications

Pinout & Package

Package: 7×7 mm, 56-pin QFN (MLF), exposed thermal pad, RoHS-compliant - optimized for high-density SFP transceiver modules with efficient thermal dissipation.

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-IMR/F uniquely integrates adaptive equalization, G.703-compliant CMI driver, and dual-path CDR in a single 56-pin QFN - delivering true plug-and-play STM-1e LIU functionality without supplemental ICs or layout modifications.

Availability

The 78P2351R-IMR/F is available at Aetrix Electronics and suitable for STM-1e SFP modules, SDH/ATM line cards, and add-drop multiplexers requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for 78P2351R-IMR/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, powerline communications, and telecom interface solutions before its acquisition by Maxim Integrated in 2010.

The 78P2351R-IMR/F belongs to Teridian's second-generation LIU product line, engineered specifically for cost-sensitive, space-constrained STM-1e electrical interface applications in carrier-class SFP modules and SDH infrastructure equipment.

FAQ

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

The 78P2351R-IMR/F functions as a complete Line Interface Unit that converts LVPECL-encoded NRZ data to ITU-T G.703-compliant CMI signals for 155.52 Mbps coaxial transmission, while simultaneously recovering clock and data from incoming CMI signals. It integrates dual CDRs, adaptive equalization, and configurable timing modes - all within a single 56-pin QFN package - making it ideal for SFP modules and SDH line cards.

Does the 78P2351R-IMR/F require an external clock source, and what frequencies are supported?

Yes, the 78P2351R-IMR/F requires an external reference clock applied to CKREFP/N pins. It supports three frequencies: 19.44 MHz (CMOS, CKREFN tied to ground), 77.76 MHz (CMOS, CKREFN grounded), and 155.52 MHz (differential LVPECL). Frequency selection is controlled by the CKSL[1:0] bits or CKSL pin state, and the internal PLL uses this reference to generate the 311.04 MHz clock for CMI encoding.

How does the 78P2351R-IMR/F handle degraded coaxial signal quality due to cable loss?

The 78P2351R-IMR/F handles degraded coaxial signals using an integrated adaptive equalizer in the receive path that compensates for >12.7 dB of cable loss and associated inter-symbol interference. Additionally, Receiver Monitor Mode adds 20 dB of flat gain pre-equalization - enabling reliable operation at monitoring points with up to 6 dB of coax loss - while Rx LOS detection remains disabled during this mode.

Can the 78P2351R-IMR/F operate in both hardware and software configuration modes?

Yes, the 78P2351R-IMR/F supports dual configuration modes: hardware mode (SPSL pin low) uses dedicated control pins like CKMODE, TXPD, and LPBK for basic setup; software mode (SPSL pin high) enables full register-level control via a 4-wire serial interface (SEN, SCK_MON, SDI, SDO) operating up to 20 MHz. Both modes allow independent Tx/Rx power-down, loopback activation, and timing mode selection.

What packaging and thermal specifications apply to the 78P2351R-IMR/F?

The 78P2351R-IMR/F is housed in a 7×7 mm, 56-pin QFN (MLF) package with an exposed thermal pad, rated for industrial temperature operation from −40°C to +85°C. Its single 3.3 V supply and integrated thermal design enable reliable performance in thermally constrained SFP modules and dense line card layouts without auxiliary cooling.