Diodes Incorporated ZC835BTC

Overview

ZC835BTC from Zetex Semiconductors is a silicon hyperabrupt varactor diode optimized for voltage-controlled frequency tuning in precision oscillators. It delivers 68.0 pF nominal capacitance at 2 V, 5.0–6.5 capacitance ratio (C₂/C₂₀), and 100 minimum Q at 50 MHz, enabling low-phase-noise VCXO/TCXO designs in SOT23 surface-mount packages.

For engineers reviewing the ZC835BTC datasheet, ZC835BTC pinout, ZC835BTC application, or ZC835BTC equivalent, key selection criteria include its 61.2–74.8 pF capacitance range at 2 V, <20 nA reverse leakage at 20 V, −55°C to +150°C operating temperature, and suitability for wireless transceiver tuning circuits requiring steep CV slope and high Q.

Technical Context

The ZC835BTC is a single-die, hyperabrupt junction varactor engineered for steeper capacitance-voltage (CV) slope than standard abrupt diodes-critical for wide-tuning-range, low-distortion oscillator designs. Its 300–400 ppm/°C temperature coefficient of capacitance and 25 V reverse breakdown support stable operation in temperature-varying RF front-ends.

Designed specifically for analog voltage-controlled tuning, it operates with zero forward bias and relies on reverse-biased junction depletion width modulation. The device exhibits tightly controlled CV tolerance (±5% typical), low IR (200 pA typ.), and minimal series resistance-enabling high-Q resonance in LC tank circuits up to 50 MHz.

Key Specifications

Pinout & Package

SOT23 package: 3-terminal plastic surface-mount case with cathode-marked lead (Pin 1), anode (Pin 2), and cathode (Pin 3) in common-cathode dual configuration - though ZC835BTC is a single varactor die, its marking and pinout follow SOT23 standard orientation with Pin 1 as cathode.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV2023-011LF and BBY58-02W, ZC835BTC uniquely balances mid-range capacitance (68 pF), moderate Q (100), and tight CV slope control-making it optimal for VCXOs needing both 10–15 ppm tuning resolution and sub-−135 dBc/Hz phase noise at 10 kHz offset.

Availability

ZC835BTC is available at Aetrix Electronics and suitable for VCXO design, TCXO compensation networks, and wireless transceiver VCO tuning requiring stable component supply across extended temperature ranges and high-reliability RF production.

Supply support for ZC835BTC 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 and TS16949-certified designer and manufacturer of high-performance analog and RF semiconductors, acquired by Diodes Incorporated in 2008.

The 830 series varactors-including ZC835BTC-were developed for precision frequency control in communications infrastructure, targeting low-phase-noise oscillator designs where CV linearity and repeatability were critical.

FAQ

What is the maximum recommended reverse voltage for continuous operation of ZC835BTC?

The absolute maximum reverse voltage is 25 V, but Zetex specifies derated operation at ≤20 V for long-term reliability. At 20 V, reverse leakage remains ≤20 nA, preserving tuning linearity and minimizing thermal runaway risk in sealed oscillator cavities.

Does ZC835BTC require external biasing circuitry for typical VCXO use?

Yes-it requires a high-impedance, low-noise DC bias source (typically 100 kΩ–1 MΩ series resistance) to apply tuning voltage to the anode. A 10 nF ceramic bypass capacitor between anode and cathode is recommended to suppress RF feedthrough and stabilize the control node.

How does the SOT23 package affect thermal performance in high-Q oscillator designs?

The SOT23 package has a junction-to-ambient thermal resistance of ~250°C/W. In continuous 50 MHz RF environments, self-heating is negligible (<0.1°C rise), preserving CV stability-unlike larger packages where thermal gradients induce capacitance hysteresis.

Can ZC835BTC be used in place of ZC835ATA in existing designs?

Yes-ZC835BTC and ZC835ATA share identical electrical specs and SOT23 packaging; the "TC" suffix denotes 13-inch tape-and-reel (10,000 units/reel) versus "TA" (7-inch, 3,000 units/reel). No layout or schematic changes are required for substitution.