Diodes Incorporated ZC933ATC

Overview

ZC933ATC 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 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 (≈4:1) from 0–6 V. Used in wireless transceivers requiring low phase noise and stable CV tracking.

For engineers reviewing the ZC933ATC datasheet, ZC933ATC pinout, ZC933ATC application, or ZC933ATC equivalent, key selection criteria include its hyperabrupt junction profile, 12 V breakdown rating, SOT23 package footprint, C-V linearity across 0–6 V, and suitability for RF frequency synthesis in mobile radio and pager front-ends.

Technical Context

This varactor operates as a voltage-dependent capacitor where applied reverse bias modulates depletion width and junction capacitance. Its hyperabrupt doping profile ensures near-linear frequency vs. voltage response in VCOs, critical for wide-tuning-range oscillators.

Designed for RF signal path integration, it exhibits low IR (≤100 nA @ 8 V) to minimize phase noise contribution and high Q (≥150 @ 50 MHz) to preserve resonator efficiency in TCXO tank circuits.

Key Specifications

Pinout & Package

SOT23 package: 3-pin surface-mount plastic case with anode, cathode, and unused terminal (cathode common in dual variants; ZC933ATC is single diode). Standard JEDEC MO-215 outline, 2.71 mm max height, 1.37 mm max width, 1.77 mm max length.

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, ZC933ATC offers the widest usable tuning range (octave) in SOT23 while balancing Q and leakage-making it optimal for wideband industrial VCOs where both range and phase noise matter.

Availability

ZC933ATC is available at Aetrix Electronics and suitable for VCXO design, TCXO compensation networks, pager RF synthesizers, and mobile radio transmitter VCOs requiring stable component supply across extended production cycles.

Supply support for ZC933ATC 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 Diodes Incorporated) was a UK-based designer of high-performance analog and RF semiconductors, focused on precision discrete components for communications infrastructure.

ZC933ATC belongs to the ZC93x hyperabrupt varactor family, engineered specifically for low-phase-noise frequency control in wireless timing and synthesis applications from 1–1000 MHz.

FAQ

What is the maximum recommended reverse voltage for continuous operation?

The absolute maximum reverse voltage is 12 V, but continuous operation above 8 V increases leakage current and accelerates long-term parameter drift. For reliable 10+ year TCXO service life, Zetex recommends limiting VR to ≤6 V during normal tuning, reserving 12 V only for transient stress testing.

Can ZC933ATC be used in series or parallel configurations?

Yes-ZC933ATC supports series connection (anode-to-anode) to halve effective capacitance and improve voltage handling, or parallel connection (cathode-to-cathode) to double capacitance. However, parallel use requires matched units to avoid current imbalance; Zetex specifies ±10% C tolerance at 1 V and 4 V to support this.

Is the SOT23 pinout compatible with ZC933TA?

Yes-ZC933ATC and ZC933TA share identical SOT23 pinout (anode on Pin 1, cathode on Pin 2, NC on Pin 3), same die, and same electrical specs. The "C" suffix denotes tape-and-reel packaging (3,000 pcs/reel, 8 mm tape), while "TA" indicates standard tape-and-reel with same reel size and orientation.

How does temperature affect capacitance tracking in ZC933ATC?

Temperature coefficient of capacitance is +300 to +400 ppm/°C at 3 V and 1 MHz. This positive drift partially offsets negative crystal frequency drift in TCXOs, enabling simpler analog compensation networks without active thermistors or DACs in cost-sensitive designs.