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Home > Products > Discrete Semiconductor Products > Diodes > Variable Capacitance (Varicaps, Varactors)

Diodes Incorporated ZC931TA

Name: ZC931TA
Brand: Diodes Incorporated
SKU: ZC931TA
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZC931TA

Manufacturer:: Diodes Incorporated

Category:: Variable Capacitance (Varicaps, Varactors)

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: ZC931TA.pdf

Description:: DIODE VAR CAP 14.5PF 1A SOT23-3

Quantity:: RFQ Add To RFQ list

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Inventory:5,701

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Product details

Overview

ZC931TA from Zetex Semiconductors is a 12 V hyperabrupt silicon varactor diode in SOT23 package, optimized for voltage-controlled oscillators (VCXOs) and temperature-compensated crystal oscillators (TCXOs). It delivers 13.5 pF capacitance at 1 V, 6.5 pF at 2.5 V, and 4.0 pF at 4 V reverse bias, with minimum Q of 300 at 50 MHz and typical reverse leakage of 200 pA - enabling ultra-low phase noise in frequency tuning circuits for wireless transceivers.

For engineers reviewing the ZC931TA datasheet, ZC931TA pinout, ZC931TA application, or ZC931TA equivalent, key selection criteria include its octave-tuning range (0–6 V), tight C-V tolerance, high Q at RF frequencies, low IR for minimal oscillator noise floor degradation, and compatibility with miniature SMT layouts in timing modules and mobile radio front-ends.

Technical Context

The ZC931TA employs a hyperabrupt junction profile to achieve near-linear frequency vs. voltage response over 0–6 V tuning range, critical for stable VCXO pullability. Its capacitance ratio C_1V/C_4V = 13.5/4.0 ≈ 3.4 supports >1-octave frequency coverage without external compensation networks.

Designed for RF tuning applications up to 50 MHz, it maintains Q ≥ 300 at 4 V bias and 50 MHz, with temperature coefficient of capacitance specified at +300 to +400 ppm/°C - enabling predictable drift compensation in TCXO reference loops.

Key Specifications

Parameter	Value and Actual Design Meaning
C_1V	13.5 pF - sets nominal oscillator center frequency at low bias
C_2.5V	6.5 pF - enables mid-range tuning point for ±50 ppm TCXO adjustment
C_4V	4.0 pF - defines high-bias capacitance limit for maximum frequency excursion
Q_min @ 4V, 50 MHz	300 - ensures <0.33% insertion loss in resonator tank, preserving phase noise
I_R @ 8V	0.2–100 nA - guarantees sub-200 pA typical leakage, minimizing bias current-induced jitter
V_BR	12 V - establishes absolute maximum tuning voltage without breakdown risk
TC_C	+300 to +400 ppm/°C - allows accurate thermal drift modeling in oscillator compensation algorithms

Pinout & Package

SOT23 package: 3-pin surface-mount plastic case with anode-cathode-anode (dual common cathode) configuration; compact footprint (2.67 × 1.20 mm) suitable for high-density RF PCBs.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Anode 1	First varactor junction anode; connects to tuning voltage node in VCXO loop
Pin 2	Cathode (common)	Shared cathode for both diodes; ties to ground or resonator cold end
Pin 3	Anode 2	Second varactor anode; enables dual-tuning or balanced configuration

Key Features

Feature	Design Value
Hyperabrupt junction profile	Enables linearized f–V tuning curve across 0–6 V, reducing need for DAC nonlinearity correction
Octave tuning range	Supports >100% frequency span (e.g., 10–20 MHz) with single diode in fundamental-mode oscillator
Low I_R (200 pA typ.)	Minimizes bias-current-induced phase modulation, critical for <−160 dBc/Hz close-in phase noise
High Q (300 min @ 50 MHz)	Reduces resonator losses, improving oscillator short-term stability and reducing power consumption
Tight C–V tolerance	Ensures consistent pullability across production lots, simplifying TCXO calibration routines

Applications

VCXO Frequency Tuning

TCXO Temperature Compensation

Use Scenario: Voltage-controlled crystal oscillator in base station reference clock module requiring ±5 ppm tuning over −40°C to +85°C.

IC Role / Device Role / Timing Role: Varactor diode providing variable reactance in Pierce oscillator tank to adjust crystal load capacitance dynamically.

Use Value: Enables precise digital frequency pulling via DAC-driven bias voltage while maintaining Q > 250 at operating point.

Use Scenario: Temperature-compensated crystal oscillator for GPS receiver local oscillator with 0.1 ppb/°C stability target.

IC Role / Device Role / Timing Role: Dual common-cathode varactor pair used in analog compensation network to counteract crystal C₀ drift.

Use Value: Matched C–V tracking between two diodes reduces residual temperature error in closed-loop compensation.

Mobile Radio Transceiver

Wireless Pagers

Use Scenario: UHF band synthesizer VCO in handheld two-way radio requiring fast lock time and low spurious output.

IC Role / Device Role / Timing Role: Primary tuning element in 400–470 MHz VCO core, biased through low-noise op-amp filter.

Use Value: High Q and low IR suppress harmonic distortion and phase noise sidebands within 10 kHz offset.

Use Scenario: Paging receiver IF oscillator operating at 455 kHz with battery-powered 10-year service life.

IC Role / Device Role / Timing Role: Low-power varactor in LC-tuned oscillator, biased from micropower LDO.

Use Value: 200 pA typical I_R extends battery life by minimizing standby current in always-on timing circuit.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SMV1232-011	C_1V = 12.5 pF, Q = 250 @ 50 MHz, I_R = 500 pA max	Lower Q and higher leakage reduce phase noise margin in high-stability VCXOs	Preferred for cost-sensitive consumer radios where ±10 ppm stability suffices
BBY52-02W	C_1V = 14.5 pF, Q = 280 @ 50 MHz, hyperabrupt but no dual-cathode option	Lacks common-cathode dual-diode configuration, limiting TCXO compensation topology options	Used when single-junction tuning suffices and board space permits discrete layout

Compared with SMV1232-011 and BBY52-02W, ZC931TA offers superior Q and lower leakage for demanding oscillator designs, while its dual common-cathode structure uniquely supports matched-pair compensation - making it irreplaceable in precision TCXOs despite narrower industry availability.

Availability

ZC931TA is available at Aetrix Electronics and suitable for VCXO design, TCXO manufacturing, and mobile radio transceiver development requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ZC931TA 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, specializing in low-noise, high-speed, and precision devices for communications infrastructure.

The ZC931TA belongs to Zetex's ZC93x series of hyperabrupt varactors - engineered specifically for low-phase-noise frequency control in telecom timing modules and portable wireless equipment.

FAQ

What is the maximum recommended reverse voltage for continuous operation?

The absolute maximum reverse voltage is 12 V, but for reliable long-term operation in VCXOs, Zetex specifies 8 V as the maximum applied tuning voltage. At 8 V, reverse leakage remains ≤100 nA, and capacitance change stabilizes - exceeding this risks accelerated aging and irreversible C–V shift due to junction stress.

Does ZC931TA support dual-diode operation in a single package?

Yes - ZC931TA uses a dual common-cathode configuration in SOT23: Pin 1 and Pin 3 are independent anodes sharing Pin 2 as the common cathode. This allows matched-pair tuning in TCXOs or differential VCO topologies without inter-device tracking errors.

How does temperature affect capacitance tuning linearity?

Capacitance exhibits a +300 to +400 ppm/°C temperature coefficient at 3 V bias and 1 MHz. While C–V slope remains stable across −40°C to +85°C, absolute capacitance shifts linearly - requiring either temperature-sensing bias compensation or factory calibration tables in digital TCXOs.

Can ZC931TA be substituted with ZC930TA in existing designs?

No - ZC930TA has C_1V = 8.7 pF and C_4V = 2.9 pF, yielding only ~3× capacitance ratio versus ZC931TA's ~3.4×. Substitution alters tank impedance, degrades Q, and reduces tuning range by ~15%, requiring full oscillator re-characterization and potential loop filter redesign.

ZC931TA Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Capacitance @ Vr, F:: 4pF @ 4V, 50MHz

Capacitance Ratio:: -

Capacitance Ratio Condition:: -

Voltage - Peak Reverse (Max):: 12 V

Diode Type:: Single

Q @ Vr, F:: 300 @ 4V, 50MHz

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

ZC931TA FAQ

1.How can I place an order for ZC931TA through Aetrix?

Please submit a Request for Quotation (RFQ) for ZC931TA on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for ZC931TA reliable?

The price and inventory of ZC931TA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZC931TA is usually 5 days.

3.What payment methods are accepted for ZC931TA?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZC931TA transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZC931TA?

ZC931TA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZC931TA order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for ZC931TA?

For technical support, including ZC931TA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZC931TA requirements.

6.How does Aetrix verify that ZC931TA is sourced from the original manufacturer or authorized distributors?

All ZC931TA products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that ZC931TA meets industry standards.

7.What is the process for return or replacement of ZC931TA?

All ZC931TA units undergo pre-shipment inspection (PSI). If there is an issue with ZC931TA, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The ZC931TA part is unused and in its original packaging.

Return procedure for ZC931TA:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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