Analog Devices Inc./Maxim Integrated MAX3681EAG

Overview

MAX3681EAG from Maxim Integrated is a 1:4 deserializer IC designed for SDH/SONET and ATM transmission systems, converting 622Mbps PECL serial data to 4-bit-wide 155Mbps LVDS parallel data. It operates from a single +3.3V supply, features differential PECL inputs (SD+/−, SCLK+/−), LVDS outputs (PCLK+/−, PD0–PD3+/−), and an LVDS synchronization input (SYNC+/−) for realignment and reframing.

For engineers reviewing the MAX3681EAG datasheet, MAX3681EAG pinout, MAX3681EAG application, or MAX3681EAG equivalent, key selection considerations include its 24-pin SSOP package, −40°C to +85°C operating range, 622MHz serial clock support, LVDS output compliance, and synchronization-enabled bit alignment control in telecom timing-critical interfaces.

Technical Context

The MAX3681EAG implements a 4-bit shift register clocked by PECL serial clock (SCLK), a 2-bit counter dividing SCLK by four to generate PCLK, and a parallel output register latching data on PCLK's rising edge. Its architecture enables deterministic 1:4 serialization/deserialization with precise timing relationships defined in Figures 2 and 3 of the datasheet.

LVDS I/Os comply with IEEE 1596.3, using 100Ω differential termination for outputs and internal 100Ω termination for SYNC inputs. PECL inputs require external 50Ω termination to (VCC − 2V), supporting interoperability with standard PECL sources in optical line card and add/drop multiplexer signal paths.

Key Specifications

Pinout & Package

MAX3681EAG is housed in a 24-pin SSOP (Shrink Small Outline Package) with 0.65mm lead pitch, JEDEC MO-150 compliant, dimensions 7.65mm × 5.38mm × 1.99mm (L × W × H). Pin 1 is located at top-left corner with dot marking; leads are coplanar within 0.10mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX3675 and MAX3664, the MAX3681EAG uniquely balances OC-12-specific performance, LVDS synchronization capability, and minimal footprint-making it optimal for cost-sensitive, fixed-rate SDH/SONET receive-path designs where CDR is handled externally.

Availability

MAX3681EAG is available at Aetrix Electronics and suitable for 622Mbps SDH/SONET transmission systems, ATM/SONET access nodes, and digital cross-connect equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX3681EAG 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) is a U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and RF solutions for communications, computing, and industrial markets.

The MAX3681EAG belongs to Maxim's high-speed communications interface product line, engineered specifically for SDH/SONET physical-layer signal conditioning and protocol translation in telecom infrastructure equipment.

FAQ

What is the maximum serial clock frequency supported by the MAX3681EAG?

The MAX3681EAG supports a maximum serial clock frequency of 622MHz, corresponding to 622Mbps data rate. This is specified across the full operating temperature range (−40°C to +85°C) and validated under VCC = +3.0V to +3.6V conditions. The device maintains timing margins per AC Electrical Characteristics table, including tSU = 800ps minimum setup time and tH = 50ps minimum hold time at TA = +25°C.

Does the MAX3681EAG include built-in clock recovery functionality?

No, the MAX3681EAG does not include clock recovery. It is a deserializer only and requires a clean, low-jitter PECL serial clock (SCLK+/−) to be supplied externally. Clock recovery must be implemented upstream-e.g., using a separate CDR IC such as the MAX3664-or provided by the optical receiver module feeding the MAX3681EAG.

How is data realignment performed on the MAX3681EAG?

Data realignment on the MAX3681EAG is triggered by pulsing the LVDS SYNC+/− inputs high for at least two SCLK cycles. This causes the parallel output register to delay data by one bit position, dropping the first bit of the current PCLK cycle. The realignment completes within two PCLK cycles of the SYNC signal's rising edge, ensuring deterministic behavior for hitless protection switching in SONET networks.

What termination is required for the LVDS outputs of the MAX3681EAG?

The LVDS parallel clock (PCLK+/−) and data outputs (PD0–PD3+/−) of the MAX3681EAG require external 100Ω differential DC termination between each complementary pair. This termination must be placed at the receiver end of the transmission line-not at the MAX3681EAG output pins-and must not be grounded. Failure to apply correct termination results in signal integrity degradation and timing violations.

Is the MAX3681EAG pin-compatible with other devices in the MAX36xx family?

No, the MAX3681EAG is not pin-compatible with other MAX36xx devices. While MAX3675 shares the same 24-pin SSOP package, its pin functions differ-e.g., MAX3675 lacks SYNC inputs and has different output assignments. MAX3664 uses a 32-pin QFN package and includes additional CDR-related pins. Board-level replacement requires redesign for any alternative part.