Analog Devices Inc./Maxim Integrated MAX9421EHJ

Overview

MAX9421EHJ from Maxim Integrated is a quad differential LVECL-to-LVPECL translator in 32-pin TQFP package, delivering 336ps typical propagation delay, 17ps typical channel-to-channel skew, and integrated 50Ω series output termination. It operates with -2.0V to -3.6V negative supply and 2.375V to 3.6V positive supply, supporting high-speed clock distribution in DSLAM backplanes and base station timing subsystems.

For engineers reviewing the MAX9421EHJ datasheet, MAX9421EHJ pinout, MAX9421EHJ application, or MAX9421EHJ equivalent, this page provides verified electrical parameters, synchronous/asynchronous mode behavior, differential input/output voltage definitions, thermal resistance data, and real-world design constraints for high-frequency signal integrity.

Technical Context

The MAX9421EHJ implements four independent differential translation channels using bipolar process technology, with dual-mode operation controlled by the SEL differential pair: asynchronous mode (SEL = high) enables direct LVECL-to-LVPECL conversion per channel, while synchronous mode (SEL = low) latches all inputs on the rising edge of CLK/CLK. Each channel features open inputs requiring external biasing and integrated 50Ω series output resistors with 8.2mA internal pulldown current sources.

It supports up to 2GHz data frequency in asynchronous mode and 3.0GHz clock frequency in synchronous mode, maintaining ≥600mV differential output swing at 3.0GHz. Input common-mode range spans VEE to +0.3V, and outputs are referenced to VCC with common-mode voltage of VCC − 1.25V (typ), enabling interoperability with standard LVPECL receivers.

Key Specifications

Pinout & Package

MAX9421EHJ uses a 32-pin 5mm × 5mm TQFP package with exposed paddle connected to VEE internally. Pin layout follows standard differential signaling conventions with mirrored IN_/IN_, OUT_/OUT_, CLK/CLK, SEL/SEL, and EN/EN pairs, plus four VCC pins (pins 11, 17, 24, 30) and four GND pins (pins 14, 20, 21, 27) for low-inductance power delivery.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad differential level translation applications.

Compared with MAX9421EHJ, MAX9423EHJ adds input termination at the cost of slightly higher input capacitance, while SY100ELT23LZG trades integration and control flexibility for package compatibility-making MAX9421EHJ optimal for new high-density, high-speed clock distribution designs requiring quad-channel coordination.

Availability

MAX9421EHJ is available at Aetrix Electronics and suitable for DSLAM backplane clock distribution, base station timing subsystems, and central office clock fanout requiring stable component supply across extended product lifecycles.

Supply support for MAX9421EHJ 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 semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and computing markets.

The MAX9420–MAX9423 family was designed specifically for ultra-low-skew, high-frequency clock and data translation in telecom infrastructure, targeting applications demanding sub-100ps timing alignment and GHz-range bandwidth.

FAQ

What is the maximum clock frequency supported by MAX9421EHJ in synchronous mode?

The MAX9421EHJ supports a maximum clock frequency of 3.0GHz in synchronous mode (SEL = low), verified with ≥500mV differential output swing and 0.53ps RMS added random jitter. This specification is measured with CLK/CLK inputs terminated differentially and outputs loaded with 50Ω to VCC − 2.0V, per the AC Electrical Characteristics table.

Does MAX9421EHJ require external termination on its inputs?

Yes, MAX9421EHJ has open inputs and requires external differential biasing. As shown in Figure 5 of the datasheet, unused inputs must be terminated with a 100Ω resistor across IN_/IN_ and biased to VEE using 1kΩ resistors to ensure stable DC operating points and prevent noise-induced switching.

How does the enable function operate on MAX9421EHJ?

The MAX9421EHJ uses a differential enable pair (EN/EN): when EN = high and EN = low (differential high), outputs are active; when EN = low and EN = high (differential low), all four output pairs are forced to a differential low state regardless of input or clock activity. This hard disable prevents false triggering during power sequencing.

Can MAX9421EHJ operate with a 3.3V positive supply and -3.3V negative supply?

Yes, MAX9421EHJ is fully specified for VCC = 3.3V and VEE = -3.3V, which falls within its rated ranges of 2.375V to 3.6V (VCC) and -2.0V to -3.6V (VEE). At these supplies, it delivers 660mV typical differential output swing and 336ps typical propagation delay, matching key performance benchmarks in the datasheet.

What is the thermal resistance of MAX9421EHJ in its TQFP package?

The MAX9421EHJ in 32-pin TQFP has a junction-to-ambient thermal resistance of +105°C/W in still air, and +73°C/W with 500 LFPM airflow. Its junction-to-case thermal resistance is +25°C/W, enabling reliable operation at full speed under +85°C ambient conditions when properly heatsinked or airflow-cooled.