Diodes Incorporated ZC829ATA

Overview

ZC829ATA from Zetex Semiconductors is a silicon hyperabrupt varactor diode optimized for voltage-controlled frequency tuning in precision oscillators and RF filters. It delivers 8.2 pF nominal capacitance at 2 V, 4.3–5.8 capacitance ratio (C₂/C₂₀), ≥250 Q at 50 MHz, and ultra-low reverse leakage (200 pA typ.), enabling low-phase-noise VCXO/TCXO designs in wireless infrastructure and mobile radio front-ends.

For engineers reviewing the ZC829ATA datasheet, ZC829ATA pinout, ZC829ATA application, or ZC829ATA equivalent, key selection criteria include its hyperabrupt CV slope for steep tuning response, SOT23 package compatibility with high-density RF layouts, 25 V reverse breakdown rating, and guaranteed 250 MHz minimum self-resonant frequency in matching networks.

Technical Context

The ZC829ATA employs a hyperabrupt junction profile to achieve a steep, linearized C–V curve-critical for minimizing tuning nonlinearity in voltage-controlled crystal oscillators. Its capacitance varies from ~8.2 pF at 2 V to ~1.4 pF at 20 V, yielding a measured C₂/C₂₀ ratio of 4.3–5.8 under 1 MHz test conditions.

Designed for RF signal path integration, it maintains Q ≥ 250 at 50 MHz and 3 V bias, ensuring minimal insertion loss in bandpass and notch filter topologies. The device operates across –55 °C to +150 °C and exhibits a temperature coefficient of capacitance of 300–400 ppm/°C, supporting stable performance in thermally varying environments.

Key Specifications

Pinout & Package

Supplied in SOT23 package (JEDEC TO-236AB), with cathode-marked lead configuration. Pin 1 = Anode, Pin 2 = Cathode, Pin 3 = Cathode (common-cathode dual variant not applicable to ZC829ATA; this is a single-diode variant).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV2023-011LF and BBY52-02W, ZC829ATA uniquely balances wide tuning ratio, high breakdown, and SOT23 compatibility-making it optimal for 12 V VCXOs needing both range and ruggedness without sacrificing layout density.

Availability

ZC829ATA is available at Aetrix Electronics and suitable for VCXO design, RF filter tuning, and mobile radio transceiver development requiring stable component supply and traceable lot-level qualification.

Supply support for ZC829ATA 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 was a UK-based ISO 9001/TS16949-certified designer and manufacturer of high-performance analog and RF semiconductors, acquired by Diodes Incorporated in 2008.

The 830 series varactors were engineered specifically for precision frequency control in wireless timing systems-emphasizing CV linearity, low leakage, and thermal stability in compact SMT packages.

FAQ

What is the maximum recommended reverse voltage for continuous operation?

The ZC829ATA has a rated reverse breakdown voltage of 25 V minimum, with absolute maximum rating of 25 V. For reliable long-term operation, Zetex specifies ≤20 V reverse bias in continuous service to maintain leakage below 20 nA and avoid junction degradation over temperature cycling.

Does ZC829ATA require external bias decoupling in VCO applications?

Yes-Zetex recommends a 100 nF ceramic capacitor placed within 2 mm of the cathode pin (Pin 2) to suppress control-line noise. This prevents AM-to-PM conversion that degrades phase noise; the SOT23 package's low inductance makes effective local decoupling essential for sub-–130 dBc/Hz performance.

Is the SOT23 marking "J9A" sufficient for full traceability?

Yes-"J9A" is the official Zetex device marking for ZC829ATA, corresponding to the "829A" capacitance grade (7.38–9.02 pF). Full traceability includes reel code TA (7-inch tape), date code, and lot number on packaging; all are retained in Aetrix's certified distribution chain.

Can ZC829ATA be used in DC-coupled tuning circuits?

No-ZC829ATA must operate under reverse bias only. DC coupling risks forward conduction, causing irreversible junction heating and parametric shift. All applications require AC coupling or dedicated bias-T networks to isolate RF and DC paths while maintaining ≥2 V reverse bias across the junction.