Diodes Incorporated ZC930TA

Overview

ZC930TA from Zetex Semiconductors is a silicon hyperabrupt varactor diode optimized for voltage-controlled oscillator (VCO) and crystal oscillator (VCXO/TCXO) tuning circuits. It delivers 8.7 pF capacitance at 1 V, 4.3 pF at 2.5 V, and 2.9 pF at 4 V reverse bias, with minimum Q of 200 at 50 MHz and typical reverse leakage of 200 pA - enabling ultra-low phase noise in precision frequency control applications.

For engineers reviewing the ZC930TA datasheet, ZC930TA pinout, ZC930TA application, or ZC930TA equivalent, key selection criteria include its octave tuning range (0–6 V), tight C-V tolerance, SOT23 package compatibility, and proven use in wireless transceivers and mobile radio front-ends where phase noise and tuning linearity are critical.

Technical Context

The ZC930TA employs a hyperabrupt junction profile to achieve near-linear frequency vs. voltage response over 0–6 V, essential for stable VCXO pullability and TCXO compensation loops. Its low IR (≤100 nA max at 8 V) and high Q (≥200 @ 4 V, 50 MHz) directly suppress thermal and flicker noise contributions in oscillator tank circuits.

Designed for RF tuning in compact portable systems, it operates within a 12 V maximum reverse voltage rating and supports SOT23 surface-mount assembly. Temperature coefficient of capacitance is tightly controlled at 300–400 ppm/°C, minimizing drift across industrial temperature ranges.

Key Specifications

Pinout & Package

SOT23-3 package: compact 1.77 mm × 2.71 mm × 1.37 mm surface-mount outline with gull-wing leads; rated P_tot = 330 mW at T_amb = 25°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV1232-011LF and BBY52-02W, the ZC930TA offers superior Q and lower leakage - delivering up to 4 dB lower integrated phase noise in VCXOs - while maintaining identical SOT23 mounting and compatible biasing, making it the preferred choice for high-stability timing designs.

Availability

ZC930TA is available at Aetrix Electronics and suitable for VCXO calibration, TCXO compensation, mobile radio VCOs, and wireless transceiver front-ends requiring stable component supply with traceable lot control and full RoHS compliance.

Supply support for ZC930TA 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 discretes, with engineering heritage in precision silicon varactors and low-noise transistors.

The ZC930 series was developed specifically for telecom-grade frequency control - targeting VCXO/TCXO manufacturers needing octave-tuning capability, ultra-low phase noise, and SMT scalability in portable infrastructure equipment.

FAQ

What is the maximum recommended reverse voltage for continuous operation?

The ZC930TA has an absolute maximum reverse voltage rating of 12 V, but for reliable long-term operation in oscillators, Zetex specifies 8 V as the maximum recommended DC bias. Operating above 8 V increases reverse leakage exponentially and degrades Q, especially at elevated temperatures.

Does the ZC930TA require series current limiting in VCO applications?

No series current-limiting resistor is needed because the device operates exclusively under reverse bias. However, a high-value (≥1 MΩ) resistor is recommended between the tuning voltage source and anode to isolate RF from the control line and prevent modulation distortion in FM/FSK systems.

How does the SOT23 pinout differ from SOD323 for ZC930-series variants?

ZC930TA uses SOT23 with anode on Pin 1, cathode on Pin 2, and Pin 3 unconnected. SOD323-packaged ZMV930TA places anode on the marked end and cathode on the opposite end - no third terminal - requiring PCB footprint redesign and different thermal pad layout for equivalent RF performance.

Can ZC930TA be used in zero-bias (0 V) tuning configurations?

Yes - the hyperabrupt junction provides usable capacitance down to 0 V reverse bias (C_J ≈ 10.2 pF), enabling true zero-volt tuning in low-power wake-up oscillators. However, phase noise increases by ~3 dB below 0.5 V due to reduced depletion width and higher effective series resistance.