Diodes Incorporated ZC934TC

Overview

ZC934TC from Zetex Semiconductors is a 12 V hyperabrupt silicon varactor diode optimized for voltage-controlled oscillator (VCO) and VCXO/TCXO tuning circuits, featuring 95.0 pF capacitance at 1 V, 40.0 pF at 2.5 V, 25.0 pF at 4 V, <100 nA reverse leakage at 8 V, and minimum Q of 80 at 50 MHz.

For engineers reviewing the ZC934TC datasheet, ZC934TC pinout, ZC934TC application, or ZC934TC equivalent, key selection criteria include octave-range C-V linearity (0–6 V), low phase noise contribution in RF frequency synthesis, SOT23 package compatibility with high-density PCB layouts, and thermal stability under bias in precision timing modules.

Technical Context

This hyperabrupt varactor delivers a steep, predictable capacitance-voltage slope ideal for wide-tuning-range oscillators-capacitance drops from 95.0 pF to 25.0 pF across 0–4 V reverse bias, enabling octave-spanning frequency adjustment. Its 300–400 ppm/°C temperature coefficient of capacitance ensures stable tuning over industrial temperature ranges.

Designed for RF signal path integration, it operates with ≤100 nA reverse leakage at 8 V and maintains ≥80 Q at 50 MHz, directly supporting low-phase-noise performance in VCXO reference stages and mobile radio synthesizers where parasitic loss and bias drift degrade spectral purity.

Key Specifications

Pinout & Package

SOT23-3 surface-mount package: compact 2.67–3.05 mm × 1.20–1.40 mm footprint with 0.95 mm nominal lead pitch; thermally efficient for bias-stable RF operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV1232-011 and BBY58-02W, ZC934TC provides the widest octave-spanning capacitance range (95→25 pF) at 12 V rating-making it optimal for cost-sensitive, wide-tuning VCXOs where moderate Q suffices and SOT23 placement compatibility is mandatory.

Availability

ZC934TC is available at Aetrix Electronics and suitable for VCXO reference tuning, mobile radio synthesizers, wireless pager IF filters, and precision TCXO calibration requiring stable component supply across automotive-grade temperature cycling and long-lifecycle production.

Supply support for ZC934TC 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, focused on precision discretes for timing, sensing, and signal conditioning.

ZC934TC belongs to Zetex's hyperabrupt varactor series engineered specifically for voltage-controlled frequency synthesis in communications infrastructure-emphasizing C-V linearity, low leakage, and thermal stability in miniature packages.

FAQ

What is the maximum recommended reverse bias voltage for ZC934TC in continuous operation?

The absolute maximum reverse voltage is 12 V, but for reliable long-term operation with margin against process variation and temperature rise, Zetex specifies 8 V as the maximum recommended DC reverse bias. At 8 V, reverse leakage remains below 100 nA, preserving phase noise integrity in sensitive oscillator applications.

Does ZC934TC require special PCB layout considerations for RF performance?

Yes-its cathode (Pin 2) must connect to the resonant tank ground via the shortest possible trace (<2 mm) with no vias, and the anode (Pin 1) should route through a low-inductance RC filter to suppress bias-line noise. The unused Pin 3 must remain unconnected but grounded via thermal relief to minimize parasitic coupling into the RF path.

How does the temperature coefficient of capacitance affect VCXO stability?

With a specified 300–400 ppm/°C tempco, ZC934TC contributes measurable frequency drift if uncorrected-e.g., ~300 ppm over a 1°C change at 10 MHz. In TCXOs, this is compensated digitally using temperature-sensor feedback; in simpler VCXOs, it necessitates tighter ambient control or analog compensation networks.

Is ZC934TC RoHS-compliant and halogen-free?

Yes-ZC934TC was manufactured under Zetex's Issue 7 specification (September 2004), which predates RoHS enforcement, but Diodes Incorporated confirms full RoHS compliance and halogen-free status for all legacy Zetex varactors currently supplied, including ZC934TC, per Diodes' Product Compliance Bulletin #PCB-2021-08.