Analog Devices Inc./Maxim Integrated MAX3953UGK

Overview

MAX3953UGK from Maxim Integrated is a 9.953Gbps/10.3125Gbps 1:16 deserializer with integrated clock recovery, designed for 10Gbps Ethernet and OC192 SONET line-interface systems. It recovers clock from serial CML input, retimes data, and demultiplexes into 16-bit LVDS parallel outputs at 622Mbps/644Mbps. It operates from a single +3.3V supply, dissipates 1.5W typical, and uses a SiGe bipolar process to achieve 0.75UI_P-P high-frequency jitter tolerance.

For engineers reviewing the MAX3953UGK datasheet, MAX3953UGK pinout, MAX3953UGK application, or MAX3953UGK equivalent, key selection considerations include its OIF-compliant LVDS parallel interface, differential input range (100mV_P-P to 1.2V_P-P), reference clock options (baud rate/64 or baud rate/16), TTL-compatible LOL/SYNC_ERR status indicators, and clock holdover capability during loss-of-signal conditions.

Technical Context

The MAX3953UGK integrates a digital phase/frequency detector (PFD) and voltage-controlled oscillator (VCO) in a fully monolithic PLL architecture optimized for rapid acquisition and low-jitter clock recovery. Its dual-phase-detection system-comprising a wide-pull-in REF_PD (for initial VCO locking to reference clock) and narrow-pull-in BB_PD (for final lock to serial data)-enables robust startup under varying signal conditions.

It features a CML input amplifier with programmable termination, LVDS output drivers compliant with IEEE 1596.3, and on-chip loop filter control via FIL pin (0.047µF capacitor). The device supports two selectable data rates (9.953Gbps or 10.3125Gbps) via RATESET and two reference clock divisors (baud/64 or baud/16) via REFSET, with deterministic jitter tolerance of 0.50UI and random jitter tolerance of 0.25UI.

Key Specifications

Pinout & Package

MAX3953UGK is housed in a 10mm × 10mm, 68-pin QFN package with an exposed thermal pad (EP) that must be soldered to PCB ground for electrical integrity and thermal performance. The package supports high-speed signal routing with controlled-impedance trace design and localized decoupling.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 10Gbps deserializer with clock recovery applications.

Compared with MAX3970 and MAX3971A, the MAX3953UGK uniquely balances dual-rate support, minimal external components, and 68-pin QFN footprint-making it the preferred choice for space-constrained, multi-standard 10G line interfaces requiring field-upgradable data rate selection and robust holdover behavior.

Availability

MAX3953UGK is available at Aetrix Electronics and suitable for 10Gbps Ethernet LAN, OC192 SONET add/drop multiplexers, and digital cross-connect systems requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for MAX3953UGK 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 ICs for communications, computing, and industrial applications.

The MAX3953UGK belongs to Maxim's 10Gbps optical interconnect product line, engineered specifically for carrier-grade SONET/SDH and Ethernet physical layer interfaces demanding ultra-low jitter, deterministic latency, and seamless signal loss recovery.

FAQ

What data rates does the MAX3953UGK support, and how is rate selection implemented?

The MAX3953UGK supports two serial data rates: 9.953Gbps (OC192) and 10.3125Gbps (10G Ethernet). Rate selection is controlled by the TTL-level RATESET pin: connecting RATESET to GND selects 9.953Gbps, while connecting it to VCC selects 10.3125Gbps. This hardware-selectable configuration eliminates firmware dependency and ensures deterministic startup timing for the MAX3953UGK in mission-critical telecom links.

How does the MAX3953UGK handle loss-of-signal conditions, and what role does LOS_IN play?

The MAX3953UGK implements clock holdover during loss-of-signal events using the LOS_IN pin. When LOS_IN is driven low, the device switches PLL control from the serial data input to the REFCLK input, maintaining a stable PCLKO output. If no external LOS signal is available, LOS_IN must be tied to VCC to disable holdover. This behavior ensures continuous timing integrity for upstream devices relying on PCLKO-key for the MAX3953UGK's use in SONET protection switching applications.

What is the function of the FIL pin on the MAX3953UGK, and what capacitor value is recommended?

The FIL pin on the MAX3953UGK connects to the internal PLL loop filter and must be tied to VCC through a 0.047µF capacitor to set the loop damping ratio and ensure stable lock acquisition. This external capacitor directly influences PLL bandwidth and jitter transfer characteristics. Deviation from the recommended value risks increased acquisition time, excessive overshoot, or instability-making correct FIL capacitor selection essential for reliable MAX3953UGK operation in production systems.

Does the MAX3953UGK require external termination for its CML input, and what is the supported input voltage range?

The MAX3953UGK accepts CML input signals differentially across SDI+/SDI− with a specified range of 100mV_P-P to 1.2V_P-P. It includes internal 50Ω termination to VCC, eliminating the need for external resistors in most configurations. However, if the overhead circuit lacks internal termination, 100Ω series resistors (as shown in the typical operating circuit) are required. This flexibility simplifies board design while ensuring signal integrity for the MAX3953UGK across diverse optical receiver front-ends.

What is the significance of the SYNC_ERR and CLKSEL pins working together in the MAX3953UGK acquisition sequence?

The SYNC_ERR output and CLKSEL input form an autonomous acquisition control loop in the MAX3953UGK. When SYNC_ERR goes high (indicating VCO frequency error >500ppm from REFCLK), it pulls CLKSEL high, forcing the PLL to lock to REFCLK first. Once locked, SYNC_ERR goes low, pulling CLKSEL low to switch to BB_PD and lock to the serial data. This self-managed sequence ensures reliable, software-free startup-critical for the MAX3953UGK in unattended telecom infrastructure where manual calibration is impractical.