Analog Devices Inc./Maxim Integrated MAX3891ECB

Overview

MAX3891ECB from Maxim Integrated is a 16:1 parallel-to-serial serializer IC for SDH/SONET transmission systems, converting 16-bit wide 155.52MHz parallel data into 2.5Gbps serial output using an integrated PLL clock synthesizer. It accepts single-ended LVPECL data inputs and delivers differential LVPECL serial data (SDO±) and clock (SCLKO±) outputs, operates from a single +3.3V supply, and supports extended temperature range (–40°C to +85°C) in a 64-pin TQFP-EP package.

For engineers reviewing the MAX3891ECB datasheet, MAX3891ECB pinout, MAX3891ECB application, or MAX3891ECB equivalent, this device is selected for high-speed telecom interface design where precise jitter performance (<3ps RMS), multi-rate reference clock support (38.88–155.52MHz), and system-level loopback diagnostics via CML SLBO± outputs are critical.

Technical Context

The MAX3891ECB implements a fully integrated phase/frequency detector, loop filter, voltage-controlled oscillator, and prescaler to synthesize a stable 2.488GHz internal serial clock from four selectable external reference frequencies. Its 16-bit parallel input register latches data on the rising edge of PCLKI±, while the 16-bit shift register retimes it against the synthesized SCLKO±.

Timing integrity is maintained via controlled skew (0–4ns) between PCLKO± (2.488GHz ÷ 16 = 155.52MHz) and PCLKI±, and setup/hold windows (300ps/700ps) referenced to PCLKI+ with 1ns rise/fall time. The CML loopback outputs (SLBO±) are enabled by TTL-level SOS and drive 50Ω terminated lines with 100–400mV differential swing.

Key Specifications

Pinout & Package

Package: 64-pin TQFP with exposed pad (EP), 10mm × 10mm × 1mm body, RoHS-compliant, thermal pad soldered to PCB ground plane for electrical stability and heat dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16:1 serializer applications.

Compared with MAX3891ECB, MAX3890ECB eliminates clock synthesis complexity but increases BOM count and layout sensitivity, while DS25BR100TSQ offers higher raw speed but sacrifices SONET-specific features like multi-rate reference support, jitter compliance, and system-level loopback.

Availability

MAX3891ECB is available at Aetrix Electronics and suitable for 2.5Gbps SDH/SONET transmission systems, access node interfaces, add/drop multiplexers, and digital cross-connect equipment requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for MAX3891ECB 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) designs precision analog, mixed-signal, and high-speed interface ICs for industrial, communications, and computing applications.

The MAX3891ECB belongs to Maxim's high-speed telecom serializer family, engineered specifically for SONET/SDH OC-48 line-interface applications requiring integrated clock synthesis, low-jitter performance, and system-level diagnostics.

FAQ

What reference clock frequencies does the MAX3891ECB support?

The MAX3891ECB supports four differential LVPECL reference clock frequencies: 155.52MHz, 77.76MHz, 51.84MHz, and 38.88MHz. Selection is controlled by the CLKSET pin configuration-tied to VCC, open, 20kΩ to GND, or GND respectively. This enables flexible integration into various SONET/SDH timing hierarchies without external frequency dividers or synthesizers. The MAX3891ECB uses these inputs to generate its internal 2.488GHz serial clock via an integrated PLL.

How does the MAX3891ECB implement system loopback testing?

The MAX3891ECB provides dedicated CML loopback outputs (SLBO±) enabled by a TTL-level SOS input. When SOS is driven high, SLBO± deliver a copy of the internal serialized data path, allowing direct connection to a deserializer like the MAX3881 for end-to-end link validation. This eliminates external test equipment during manufacturing and field diagnostics. The MAX3891ECB's SLBO± outputs are internally terminated to 50Ω to VCC and require no additional biasing, simplifying loopback implementation.

What is the timing relationship between PCLKI± and PCLKO± in the MAX3891ECB?

In the MAX3891ECB, PCLKO± is the 155.52MHz output derived by dividing the internal 2.488GHz serial clock by 16. The allowable skew between PCLKO± and PCLKI± is 0ns to +4.0ns, meaning the PCLKI± rising edge must occur within that window after the PCLKO± rising edge to meet setup/hold requirements. This constraint ensures reliable latching of parallel data into the shift register. The MAX3891ECB's timing architecture guarantees this relationship across –40°C to +85°C.

Does the MAX3891ECB require external termination for its LVPECL outputs?

Yes, the MAX3891ECB's LVPECL outputs (SDO±, SCLKO±, PCLKO±) require external 50Ω termination to (VCC − 2V) for proper signal integrity and common-mode voltage compliance. The datasheet recommends either direct DC termination or Thevenin-equivalent networks (e.g., 82Ω/130Ω resistive divider) when (VCC − 2V) is unavailable. AC-coupling is permitted only when followed by appropriate DC termination. The MAX3891ECB itself does not integrate LVPECL output terminations.

What package type and thermal considerations apply to the MAX3891ECB?

The MAX3891ECB is housed in a 64-pin TQFP with exposed pad (EP), measuring 10mm × 10mm × 1mm. Its exposed thermal pad must be soldered directly to a PCB ground plane to ensure both electrical stability and thermal dissipation-critical for managing its 495mW power consumption. Thermal resistance is minimized through multiple VCC and GND pins (26 VCC, 6 GND), and the package is RoHS-compliant. The MAX3891ECB's thermal design enables reliable operation at full speed across –40°C to +85°C.