Diodes Incorporated ZMV933ATA

Overview

ZMV933ATA from Zetex Semiconductors is a silicon hyperabrupt varactor diode optimized for voltage-controlled oscillator (VCO) and temperature-compensated crystal oscillator (TCXO) tuning circuits. It delivers 42.0 pF capacitance at 1 V, 27.0 pF at 4 V, minimum Q of 150 at 50 MHz, reverse leakage ≤100 nA at 8 V, and operates up to 12 V reverse bias - enabling octave-range frequency tuning in compact wireless transceivers.

For engineers reviewing the ZMV933ATA datasheet, ZMV933ATA pinout, ZMV933ATA application, or ZMV933ATA equivalent, key selection criteria include its hyperabrupt C-V slope (enabling wide tuning ratio), low phase-noise contribution via sub-100 nA IR, SOD323 package compatibility with high-density RF layouts, and verified performance in VCXO loop filters and mobile radio front-end VCOs.

Technical Context

This varactor uses a hyperabrupt junction profile to achieve a steep, linearized capacitance-voltage relationship across 0–6 V, supporting stable octave-spanning frequency synthesis. Its low series resistance and high Q (>150 @ 50 MHz) minimize insertion loss and phase noise degradation in resonant tank circuits.

The device is rated for 12 V maximum reverse voltage and exhibits tight C-V tolerance (±10% typical), with temperature coefficient of capacitance specified at +300 to +400 ppm/°C at 3 V and 1 MHz - critical for TCXO compensation linearity and thermal stability in portable radios.

Key Specifications

Pinout & Package

SOD323 surface-mount package: 1.20–1.40 mm width, 2.67–3.05 mm length, 0.33–0.51 mm height; cathode marked by beveled edge and laser-marked "AL" top-side identifier.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV1232-011 and BBY52-02W, ZMV933ATA uniquely balances 42.0 pF initial capacitance and 150 Q to deliver octave tuning with TCXO-grade thermal tracking - making it optimal for cost-sensitive, space-constrained mobile radio VCOs where both range and spectral purity matter.

Availability

ZMV933ATA is available at Aetrix Electronics and suitable for VCXO design, mobile radio transceivers, pager IF filtering, and wireless sensor node clock generation requiring stable component supply across extended temperature and lifecycle requirements.

Supply support for ZMV933ATA 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) specialized in high-performance analog and RF discretes, with focus on low-noise, high-reliability silicon solutions for communications infrastructure and portable electronics.

ZMV933ATA belongs to the ZC930/ZMV930/ZV931 hyperabrupt varactor family, engineered specifically for precision frequency control in battery-powered wireless systems where phase noise, tuning linearity, and thermal stability are design-critical.

FAQ

What is the recommended PCB layout practice for ZMV933ATA in VCO designs?

Place ZMV933ATA adjacent to the inductor/crystal with minimal trace length (<2 mm) between cathode and tuning voltage source. Use a dedicated ground pour under the SOD323 body, connect cathode pad directly to ground plane via ≥2 thermal vias, and isolate the anode node from digital routing to prevent coupling. Avoid soldermask over cathode pad to ensure reliable thermal dissipation.

Does ZMV933ATA require derating at elevated ambient temperatures?

Yes - reverse leakage current increases exponentially above 25°C; at 85°C, I_R may reach 5 nA (still within spec), but phase noise degradation becomes measurable. Derate maximum reverse voltage to 10 V above 70°C and add 100 nF ceramic decoupling at cathode to suppress thermally induced bias ripple in TCXO loops.

Can ZMV933ATA be used in dual-common-cathode configurations?

No - ZMV933ATA is a single-diode variant (marked "AL"). The dual version is ZMV933TA (marked "AM"), which integrates two independent anodes sharing one cathode. Using ZMV933ATA in place of ZMV933TA requires discrete cathode tying and doubles board area, compromising RF isolation and thermal matching.

How does the +300 to +400 ppm/°C tempco impact TCXO compensation design?

This positive tempco closely tracks the negative parabolic tempco of AT-cut quartz crystals near room temperature, allowing direct series connection in the oscillator's load capacitance leg. It eliminates need for thermistor-based compensation networks, reducing BOM count and enabling single-layer PCB implementation for cost-sensitive consumer radios.