Analog Devices Inc./Maxim Integrated MAX2608EUT+

Overview

MAX2608EUT+ from Maxim Integrated is a monolithic intermediate-frequency (IF) voltage-controlled oscillator (VCO) in SOT23-6 package, designed for portable wireless IF stages. It operates from 300MHz to 500MHz with ±4.4% guaranteed frequency limits at VTUNE = 0.4V/2.4V, delivers −8dBm differential output power, and draws 2.7mA supply current at +2.75V - enabling compact GPS receiver and land mobile radio IF synthesis.

For engineers reviewing the MAX2608EUT+ datasheet, MAX2608EUT+ pinout, MAX2608EUT+ application, or MAX2608EUT+ equivalent, key selection considerations include its 300–500MHz tuning range, integrated varactor eliminating external tuning capacitors, differential open-collector outputs requiring external pull-up elements, and guaranteed operation across −40°C to +85°C with single +2.7V to +5.5V supply.

Technical Context

The MAX2608EUT+ implements a Colpitts-based oscillator core with on-chip varactor and feedback capacitors, requiring only an external inductor (LF = 39–180nH, Q ≥40) connected between IND and GND to set center frequency. Its tuning voltage input (TUNE) accepts 0.4V to 2.4V, delivering peak tuning gain of 14.5%/V near 0.4V.

An integrated differential output buffer provides isolation from load impedance variations and supports both differential and single-ended interfacing to mixers or prescalers. Output stage uses open-collector topology (OUT+, OUT−), requiring external pull-up resistors or inductors to VCC for DC bias and optimal power transfer.

Key Specifications

Availability

MAX2608EUT+ is available at Aetrix Electronics and suitable for GPS receivers, land mobile radio transceivers, and cellular IF synthesizers requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for MAX2608EUT+ 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 high-performance analog and mixed-signal ICs for demanding RF, power, and timing applications - emphasizing integration, low noise, and small form factor.

The MAX2605–MAX2609 family targets portable wireless IF synthesis, integrating varactors and feedback networks to eliminate external tuning components while maintaining phase-noise performance across 45–650MHz.

FAQ

What is the guaranteed frequency range of MAX2608EUT+?

The MAX2608EUT+ guarantees oscillation from 300MHz to 500MHz at VTUNE = 0.4V and 2.4V respectively, with ±4.4% tolerance relative to nominal center frequency. This range is validated using external inductors meeting Q ≥40 and LF = 39–180nH, ensuring no board-level calibration is needed in production.

Does MAX2608EUT+ require external tuning capacitors?

No - the MAX2608EUT+ integrates on-chip varactor and feedback capacitors, eliminating all external tuning capacitors. Only a single external inductor (LF) connected between IND and GND is required to set the oscillation frequency, simplifying layout and reducing BOM count.

How is the output of MAX2608EUT+ interfaced to a mixer?

The MAX2608EUT+ provides differential open-collector outputs (OUT+, OUT−) that require external pull-up elements to VCC. For mixer drive, a reactive power match (shunt inductor + series capacitor per output) delivers up to −8dBm differential power; resistive pull-ups (e.g., 1kΩ) are acceptable for lower-frequency or less demanding interfaces.

What is the recommended bypass capacitor for the TUNE pin of MAX2608EUT+?

A ≥100pF NPO ceramic capacitor must be placed directly between TUNE (pin 3) and GND (pin 2) to provide AC ground for the internal varactor cathode. X7R dielectrics are unsuitable due to voltage coefficient and loss; omitting this capacitor degrades tuning linearity and frequency stability across temperature.

What supply voltage range does MAX2608EUT+ support?

The MAX2608EUT+ operates from a single +2.7V to +5.5V supply, with supply current remaining stable across this range (2.7mA typical at +2.75V). This allows direct connection to common Li-ion battery rails or regulated 3.3V/5V system supplies without additional regulation.