Analog Devices Inc./Maxim Integrated MAX3690ECJ

Overview

The MAX3690ECJ from Maxim Integrated is an 8:1 parallel-to-serial serializer IC designed for SDH/SONET and ATM transmission systems. It converts 8-bit, 77Mbps parallel data to 622Mbps serial output using an integrated PLL, accepts TTL inputs, delivers differential 3.3V PECL output, and operates across –40°C to +85°C in a 32-pin TQFP package.

For engineers reviewing the MAX3690ECJ datasheet, MAX3690ECJ pinout, MAX3690ECJ application, or MAX3690ECJ equivalent, key selection criteria include reference clock flexibility (38.88/51.84/77.76MHz), jitter performance (11psRMS), PECL termination requirements, parallel timing constraints (tSU = 1200ps, tH = 1000ps), and single +3.3V supply operation.

Technical Context

The MAX3690ECJ implements a fully integrated phase/frequency detector, loop filter/amplifier, voltage-controlled oscillator, and programmable prescaler to synthesize a precise 622.08MHz internal serial clock from low-frequency crystal references. Its control logic enforces strict setup/hold timing windows relative to PCLKO–PCLKI skew (≤5.0ns).

It features TTL-compatible parallel data and clock interfaces (PD0–PD7, PCLKI, PCLKO, RCLK), CKSET-programmable reference clock selection, and differential PECL outputs (SD+, SD−) requiring 50Ω DC termination to (VCC − 2V), with typical power dissipation of 200mW at +3.3V.

Key Specifications

Pinout & Package

MAX3690ECJ is housed in a 32-pin Thin Quad Flat Package (TQFP) with exposed pad, optimized for high-frequency signal routing and thermal management in telecom line cards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX3691ECJ and ICS8430M-01LFT, the MAX3690ECJ uniquely integrates reference clock selection and PLL synthesis in a PECL-output serializer, enabling direct crystal-to-622Mbps conversion without external timing components-critical for space-constrained telecom modules.

Availability

MAX3690ECJ is available at Aetrix Electronics and suitable for 622Mbps SDH/SONET transmission systems, ATM/SONET access nodes, add/drop multiplexers, and digital cross connects requiring stable component supply across extended temperature ranges.

Supply support for MAX3690ECJ 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 communication ICs for demanding industrial, telecom, and computing applications.

The MAX3690ECJ belongs to Maxim's high-speed serializer product line, engineered specifically for SDH/SONET OC-12 and ATM physical-layer interfacing with integrated clock synthesis and TTL/PECL signal conditioning.

FAQ

What reference clock frequencies does the MAX3690ECJ support?

The MAX3690ECJ supports three standard reference clock frequencies: 38.88MHz, 51.84MHz, and 77.76MHz. Selection is controlled by the CKSET pin configuration-open for 77.76MHz, grounded for 38.88MHz, or pulled to GND through a 20kΩ resistor for 51.84MHz. This enables the MAX3690ECJ to serve OC-3, OC-12, and STM-1/4 systems without hardware redesign.

How is the MAX3690ECJ's 622Mbps serial clock generated?

The MAX3690ECJ generates its 622.08MHz serial clock internally using a fully integrated PLL that locks to the external RCLK input. The PLL includes a phase/frequency detector, loop filter/amplifier, voltage-controlled oscillator, and programmable prescaler. This eliminates the need for an external 622MHz oscillator and ensures jitter performance compliant with SONET OC-12 specifications.

What are the PECL output termination requirements for the MAX3690ECJ?

The MAX3690ECJ's SD+ and SD− PECL outputs require 50Ω DC termination to (VCC − 2V), typically implemented with two 50Ω resistors to a common bias point. Alternative Thevenin-equivalent termination (e.g., 130Ω to VCC and 82Ω to GND) may be used if (VCC − 2V) is unavailable. AC coupling capacitors must be placed after the DC termination network to preserve common-mode stability.

What is the purpose of the FIL+ and FIL− pins on the MAX3690ECJ?

The FIL+ and FIL− pins on the MAX3690ECJ connect to the internal PLL loop filter. A 1µF capacitor must be placed between FIL− and VCC to stabilize the VCO control voltage, suppress phase noise, and ensure low-jitter 622MHz clock generation. Incorrect or missing filtering degrades random jitter performance beyond the specified 11psRMS limit.

Does the MAX3690ECJ provide a clock output for overhead management circuits?

Yes, the MAX3690ECJ provides a TTL-compatible PCLKO output (Pin 11) derived by dividing the internal 622.08MHz serial clock by eight, yielding a 77.75MHz clock. This output is intended to synchronize overhead generation or extraction logic, ensuring deterministic timing alignment with the serialized data stream and reducing system-level clock domain crossing complexity.