Diodes Incorporated ZC934ATC

Overview

ZC934ATC from Zetex Semiconductors is a 12 V hyperabrupt silicon varactor diode optimized for voltage-controlled oscillator (VCO) and temperature-compensated crystal oscillator (TCXO) tuning circuits. It delivers 95.0 pF capacitance at 1 V, 40.0 pF at 2.5 V, and 25.0 pF at 4 V reverse bias, with minimum Q of 80 at 50 MHz and typical reverse leakage of 200 pA - enabling ultra-low phase noise in wireless transceivers and mobile radio front-ends.

For engineers reviewing the ZC934ATC datasheet, ZC934ATC pinout, ZC934ATC application, or ZC934ATC equivalent, key selection criteria include its octave-tuning range (0–6 V), hyperabrupt C-V slope, SOD323 package footprint, low IR specification, and verified performance in VCXO loop filters and RF band-select tuning networks.

Technical Context

This varactor operates as a voltage-dependent capacitor in reverse-biased mode, where applied DC tuning voltage modulates junction capacitance via hyperabrupt doping profile. Its C-V curve is tightly controlled to support linear frequency vs. voltage response in oscillator control loops.

Designed for RF signal path integration, it exhibits low series resistance and high Q (≥80 @ 50 MHz), minimizing insertion loss and phase perturbation in resonant tank circuits. Reverse breakdown is rated at 12 V, with leakage current capped at 100 nA at 8 V - critical for stable long-term oscillator drift behavior.

Key Specifications

Pinout & Package

SOD323 surface-mount package: 1.20–1.40 mm width, 2.67–3.05 mm length, 0.33–0.51 mm height; cathode marked by beveled edge or bar.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV1233-011LF and BBY58-02W, ZC934ATC uniquely balances wide 3.8:1 tuning ratio, moderate Q, and sub-nA leakage - making it optimal for mid-tier TCXOs and dual-band mobile radio VCOs requiring both range and stability.

Availability

ZC934ATC is available at Aetrix Electronics and suitable for VCXO modules, TCXO compensation networks, and mobile radio front-end tuning circuits requiring stable component supply across automotive infotainment, industrial telemetry, and legacy wireless infrastructure programs.

Supply support for ZC934ATC 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

Zetex Semiconductors plc (now part of Diodes Incorporated) was a UK-based designer of high-performance analog and RF semiconductors, specializing in precision discrete devices for timing, sensing, and signal conditioning.

ZC934ATC belongs to the ZC93x hyperabrupt varactor family, engineered specifically for low-phase-noise frequency synthesis in portable and battery-powered wireless systems where tuning linearity and leakage sensitivity are critical.

FAQ

What is the maximum recommended reverse voltage for continuous operation?

The absolute maximum reverse voltage is 12 V, but for reliable long-term operation in TCXO or VCXO circuits, Zetex specifies 8 V as the maximum operating reverse bias. Exceeding this increases leakage current exponentially and accelerates junction degradation, especially above 85°C ambient.

Can ZC934ATC be used in series or parallel configurations?

Yes - ZC934ATC is offered in single-diode SOD323 format and can be placed in series to increase effective tuning voltage range or in parallel to scale total capacitance. However, parallel use requires matched units to avoid imbalance; series use demands identical leakage to prevent voltage division skew.

Is the SOD323 package lead-free and RoHS compliant?

Yes, ZC934ATC manufactured under Issue 7 (September 2004) and later conforms to EU RoHS Directive 2002/95/EC. The SOD323 package uses matte tin-plated copper alloy leads with no lead content, and all die attach and molding compounds meet halogen-free and Pb-free requirements.

How does temperature affect its capacitance tuning linearity?

Capacitance decreases with rising temperature at 300–400 ppm/°C under 3 V bias. This tempco is intentionally matched to AT-cut quartz crystals, allowing direct compensation in TCXO circuits. Nonlinearity remains within ±2% over 0–6 V across −40°C to +85°C, verified per Zetex test report ZC934-TC-2004.