Diodes Incorporated ZC933ATA

Overview

ZC933ATA from Zetex Semiconductors is a 12 V hyperabrupt silicon varactor diode in SOT23 package, designed for voltage-controlled frequency tuning in oscillator circuits. It delivers 42.0 pF capacitance at 1 V, 27.0 pF at 4 V, minimum Q of 150 at 50 MHz, reverse leakage ≤100 nA at 8 V, and octave tuning range (0–6 V). Used in TCXO and VCXO modules for mobile radio and wireless infrastructure.

For engineers reviewing the ZC933ATA datasheet, ZC933ATA pinout, ZC933ATA application, or ZC933ATA equivalent, key selection criteria include C-V linearity across 0–6 V, low phase noise contribution via sub-100 nA IR, Q ≥150 at 50 MHz, SOT23 thermal dissipation (330 mW), and compatibility with miniature RF bias networks.

Technical Context

This hyperabrupt junction varactor exhibits a steep, predictable capacitance-voltage slope optimized for wide-range frequency pulling in crystal oscillator loops. Its C-V curve enables octave tuning from 0 to 6 V while maintaining tight tolerance (±10% typical) between units.

Designed for RF biasing in temperature-compensated and voltage-controlled oscillators, it operates with reverse-biased junction only; forward current rating (100 mA) supports ESD robustness testing but not operational conduction. Phase noise performance is directly enabled by ultra-low IR (≤100 nA @ 8 V) and high Q factor.

Key Specifications

Pinout & Package

SOT23 package: 3-pin surface-mount plastic case with gull-wing leads; cathode marked by beveled edge and pin 1 identifier. Thermal resistance θ_JA = 300°C/W; footprint compatible with JEDEC TO-236AB standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV1232-011 and BBY52-02W, ZC933ATA offers optimal balance of octave tuning range, SOT23 thermal capability, and production-ready C-V matching-making it preferred for cost-sensitive TCXO/VCXO manufacturing rather than lab-grade OCXOs or millimeter-wave systems.

Availability

ZC933ATA is available at Aetrix Electronics and suitable for TCXO modules, VCXO-based frequency synthesizers, wireless infrastructure filters, and mobile radio transceivers requiring stable component supply across multi-year production cycles.

Supply support for ZC933ATA 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 (now part of Diodes Incorporated) specialized in high-performance analog and RF discrete semiconductors, with focus on precision timing, signal integrity, and low-noise design.

The ZC930–ZC934 series was developed specifically for frequency control applications demanding repeatable C-V characteristics, low phase noise, and miniature packaging-targeting telecom timing, portable radios, and industrial oscillator modules.

FAQ

What is the maximum recommended reverse bias voltage for continuous operation?

The absolute maximum reverse voltage is 12 V, but continuous operation should be limited to ≤6 V to maintain specified C-V linearity and avoid accelerated aging. Derating to 5 V is advised for 15+ year TCXO field life, as confirmed by Zetex reliability testing per MIL-STD-750 Method 1021.

Does ZC933ATA require external series resistance for bias network stability?

Yes-a 10 kΩ to 100 kΩ series resistor is recommended between the DAC output and anode to suppress RF feedback and prevent bias network oscillation. This value balances tuning speed (<10 µs step response) and isolation from crystal node impedance variations.

How does the SOT23 package affect thermal performance in high-density RF layouts?

SOT23 provides 330 mW power dissipation at 25°C ambient, but board-level thermal resistance rises sharply above 4-layer PCBs. For >50 mW RF dissipation, use ≥2 thermal vias under pin 2 (cathode) and 1 oz copper pour to maintain junction temperature <100°C at +85°C ambient.

Can ZC933ATA be substituted for ZC933TA without circuit modification?

Yes-ZC933ATA and ZC933TA share identical electrical specs and SOT23 pinout; the "A" suffix denotes tape-and-reel packaging (3,000 pcs/reel, TA code) versus bulk or alternate reel formats. No schematic or layout changes are needed for drop-in replacement.