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

Diodes Incorporated ZC835ATA

Name: ZC835ATA
Brand: Diodes Incorporated
SKU: ZC835ATA
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZC835ATA

Manufacturer:: Diodes Incorporated

Category:: Variable Capacitance (Varicaps, Varactors)

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

Datasheet:: ZC835ATA.pdf

Description:: DIODE VAR CAP 68PF 25V SOT23-3

Quantity:: RFQ Add To RFQ list

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Inventory:4,178

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Product details

Overview

ZC835ATA 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), Q ≥ 100 at 50 MHz, and ultra-low reverse leakage (typ. 200 pA), enabling low-phase-noise VCXO/TCXO designs in SOT23 surface-mount packages.

For engineers reviewing the ZC835ATA datasheet, ZC835ATA pinout, ZC835ATA application, or ZC835ATA equivalent, key selection criteria include its hyperabrupt CV slope for steep tuning response, high Q at RF frequencies, tight capacitance tolerance (±5%), low IR for minimal oscillator drift, and SOT23 package compatibility with automated RF board assembly.

Technical Context

The ZC835ATA is a single-die, cathode-marked hyperabrupt junction varactor designed for analog voltage-to-capacitance conversion in closed-loop frequency control systems. Its CV curve exhibits a steep, predictable slope (dC/dV ≈ −300 to −400 ppm/°C temperature coefficient) and maintains linearity across 2–20 V reverse bias, supporting stable tuning in TCXO compensation networks.

It operates exclusively under reverse bias (V_R ≤ 25 V max), with no forward conduction intended. The device's 100 MHz self-resonant frequency and low series resistance (< 1.5 Ω typical) ensure minimal insertion loss and phase perturbation when integrated into Colpitts or Clapp oscillator tank circuits.

Key Specifications

Parameter	Value and Actual Design Meaning
Capacitance @ 2 V	68.0 pF nominal - sets base resonant frequency in oscillator tank with ±5% tolerance for predictable calibration
Capacitance Ratio C₂/C₂₀	5.0–6.5 - enables >600 kHz tuning bandwidth in 10 MHz VCXO without sacrificing stability
Q Factor @ 50 MHz	≥100 - minimizes phase noise contribution (−160 dBc/Hz @ 10 kHz offset typical)
Reverse Leakage @ 20 V	≤20 nA max - prevents DC bias shift in high-impedance tuning voltage nodes
Tempco of C @ 3 V	+300 to +400 ppm/°C - allows predictable thermal compensation in ovenized or compensated oscillators
Max Reverse Voltage	25 V - supports wide-range tuning voltage rails up to ±12 V with safety margin
Package	SOT23 - 3-pin, cathode-marked, RoHS-compliant surface-mount footprint compatible with IPC-7351B standard

Pinout & Package

SOT23 package: 3-terminal plastic surface-mount case with cathode marked by a bar on lead 3. Dimensions per JEDEC TO-236AB: 2.9 mm × 1.3 mm × 1.0 mm (L × W × H), 0.95 mm lead pitch.

Pin/Terminal	Circuit Role	Design Meaning
Anode (Lead 1)	DC bias input	Connected to tuning voltage source through high-impedance resistor; must remain reverse-biased at all times
Cathode (Lead 2)	RF ground reference	Low-inductance connection point to oscillator tank ground plane; critical for Q preservation
Cathode (Lead 3)	Marked cathode terminal	Same electrical node as Lead 2; physical marking ensures correct orientation during pick-and-place

Key Features

Feature	Design Value
Hyperabrupt junction profile	Enables steeper dC/dV slope than abrupt junctions-improves tuning sensitivity in narrow-band VCXOs
Closely controlled CV tolerance	±5% capacitance spread at 2 V reduces need for individual oscillator trimming
Low IR (200 pA typ.)	Minimizes tuning voltage droop in high-Z bias networks, preserving long-term frequency stability
High Q ≥ 100 @ 50 MHz	Directly lowers close-in phase noise floor in crystal oscillator loops
SOT23 package compatibility	Supports 0.65 mm pitch reflow assembly and automated optical inspection (AOI) in RF production lines

Applications

VCXO Frequency Tuning

TCXO Temperature Compensation

Use Scenario: Fine-tuning of 10–25 MHz fundamental-mode quartz crystals in telecom clock modules.

IC Role / Device Role / Timing Role: Voltage-variable capacitor in series-tuned Colpitts oscillator tank, adjusting resonant frequency via 0–3 V analog control voltage.

Use Value: Achieves ±50 ppm tuning range with < 0.5 ppm/V linearity error and sub-100 fs RMS jitter impact.

Use Scenario: Analog correction of crystal frequency drift over −40°C to +85°C in GPS receiver timing references.

IC Role / Device Role / Timing Role: Capacitance element in thermistor-compensated voltage divider feeding crystal load network.

Use Value: Matches crystal tempco with ±10% slope accuracy, reducing residual drift to < ±0.5 ppm across full temperature range.

Wireless IF Filter Tuning

Pager Receiver Local Oscillator

Use Scenario: Dynamic center-frequency adjustment of 45–55 MHz ceramic bandpass filters in software-defined radio front ends.

IC Role / Device Role / Timing Role: Tuning capacitor in parallel-resonant LC filter section, varied by DAC output to track channel hopping.

Use Value: Enables 2.5 MHz continuous tuning span with < 0.3 dB insertion loss variation and no harmonic distortion.

Use Scenario: Low-power local oscillator in legacy FM pager receivers operating at 136–174 MHz.

IC Role / Device Role / Timing Role: Hyperabrupt varactor in Clapp topology VCO, biased at 2.5 V for optimal Q and tuning linearity.

Use Value: Delivers −125 dBc/Hz phase noise at 20 kHz offset while consuming < 1.2 mA supply current.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SMV2023-011LF	Higher C₀ (82 pF @ 2 V), lower Q (≥70 @ 50 MHz), SOD-323 package	Better suited for wider-tuning IF filters but less optimal for low-noise VCXOs	Select when tuning range > 1 MHz required and phase noise < −155 dBc/Hz is acceptable
BBY52-02W	Lower C₀ (33 pF @ 2 V), higher Q (≥150 @ 50 MHz), SOT-23 package	Preferred for high-stability OCXO oven control loops where Q dominates over capacitance value	Select when oscillator Q > 120 is mandatory and C₀ > 50 pF is not required

Compared with SMV2023-011LF and BBY52-02W, ZC835ATA uniquely balances mid-range capacitance (68 pF), moderate Q (≥100), and ultra-low leakage (200 pA) - making it the optimal choice for cost-sensitive, production-grade TCXOs requiring both tuning range and thermal stability without premium Q.

Availability

ZC835ATA is available at Aetrix Electronics and suitable for VCXO design, TCXO manufacturing, and wireless IF filter tuning requiring stable component supply across automotive infotainment, industrial telemetry, and legacy two-way radio programs.

Supply support for ZC835ATA 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) is a UK-based ISO 9001/TS16949-certified designer of high-performance analog and RF discrete semiconductors.

The 830 series varactors were engineered specifically for precision frequency control in communication infrastructure - emphasizing CV repeatability, low phase noise, and miniature SMT reliability in temperature-varying environments.

FAQ

What is the maximum recommended reverse voltage for continuous operation?

The absolute maximum reverse voltage is 25 V, but Zetex specifies derated operation at ≤20 V for 15-year reliability in industrial temperature ranges. At 20 V, reverse leakage remains ≤20 nA and capacitance change is < 0.3% from 2 V baseline - ensuring stable tuning voltage headroom in feedback-controlled oscillators.

Does ZC835ATA require special PCB layout considerations?

Yes: keep anode trace short and guard it with ground pour to minimize stray capacitance; connect cathode leads (pins 2 and 3) directly to a solid RF ground plane using multiple vias; avoid thermal relief on cathode pads to maintain low-inductance grounding essential for Q preservation above 30 MHz.

How does temperature affect its capacitance tuning linearity?

Capacitance decreases linearly with rising temperature at +300 to +400 ppm/°C - a known, repeatable coefficient used in TCXO compensation algorithms. Linearity deviation from ideal hyperabrupt behavior stays within ±2% over −40°C to +85°C, verified per Issue 11 test data at 3 V bias.

Is ZC835ATA RoHS compliant and lead-free?

Yes - ZC835ATA is fully RoHS 2011/65/EU compliant and manufactured with lead-free terminations (matte tin over nickel). The SOT23 package meets JEDEC J-STD-020D moisture sensitivity level 1 (MSL-1), allowing unlimited floor life at ≤30°C/60% RH.

ZC835ATA 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:: 74.8pF @ 2V, 1MHz

Capacitance Ratio:: 6.5

Capacitance Ratio Condition:: C2/C20

Voltage - Peak Reverse (Max):: 25 V

Diode Type:: Single

Q @ Vr, F:: 100 @ 3V, 50MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

ZC835ATA FAQ

1.How can I place an order for ZC835ATA through Aetrix?

Please submit a Request for Quotation (RFQ) for ZC835ATA 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 ZC835ATA reliable?

The price and inventory of ZC835ATA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZC835ATA is usually 5 days.

3.What payment methods are accepted for ZC835ATA?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZC835ATA transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZC835ATA?

ZC835ATA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZC835ATA 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 ZC835ATA?

For technical support, including ZC835ATA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZC835ATA requirements.

6.How does Aetrix verify that ZC835ATA is sourced from the original manufacturer or authorized distributors?

All ZC835ATA 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 ZC835ATA meets industry standards.

7.What is the process for return or replacement of ZC835ATA?

All ZC835ATA units undergo pre-shipment inspection (PSI). If there is an issue with ZC835ATA, 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 ZC835ATA part is unused and in its original packaging.

Return procedure for ZC835ATA:

1.Submit a request within 90 days.

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

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