Diodes Incorporated ZDC833ATA

Overview

ZDC833ATA from Zetex Semiconductors (now Diodes Incorporated) is a silicon dual varactor diode in SOT23 package, featuring common-cathode monolithic construction, 29.7–36.3 pF capacitance at 2 V, 5.0–6.5 capacitance ratio (2 V/20 V), and 400 ppm/°C temperature coefficient - used in voltage-controlled crystal oscillators (VCXOs) for mobile radios and cellular handsets.

For engineers reviewing the ZDC833ATA datasheet, ZDC833ATA pinout, ZDC833ATA application, or ZDC833ATA equivalent, key selection criteria include reverse voltage range (0–25 V), low leakage (<10 nA at 20 V), VHF–UHF tuning linearity, and SOT23 thermal performance up to +150°C junction temperature.

Technical Context

This dual varactor integrates two matched capacitance-tuned diodes sharing a common cathode terminal, enabling push–pull tuning in oscillator tank circuits. Its monolithic SOT23 structure ensures consistent inter-diode tracking across temperature (−55°C to +150°C) and bias conditions.

Capacitance is voltage-dependent with a defined 400 ppm/°C tempco at 3 V and 1 MHz; Q-factor exceeds 200 at 3 V/50 MHz, supporting stable phase-noise performance in VCXO loops where low-loss tuning is critical.

Key Specifications

Pinout & Package

SOT23-3 plastic surface-mount package with gull-wing leads; 1.3 mm × 2.9 mm footprint, 1.1 mm height, and JEDEC MO-178 compliant outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZDC833ATA, BBY52-02W lacks monolithic dual integration and requires external wiring, while SMV1232-011 offers superior Q but insufficient capacitance for crystal-pulling applications below 200 MHz - making ZDC833ATA uniquely suited for VHF/UHF VCXO stabilization.

Availability

ZDC833ATA is available at Aetrix Electronics and suitable for mobile radio tuning, cellular handset VCXOs, and pager frequency synthesis requiring stable component supply across extended temperature and long-lifecycle programs.

Supply support for ZDC833ATA 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, acquired by Diodes Incorporated in 2008, specialized in high-performance discrete semiconductors for RF, power management, and signal conditioning.

ZDC833ATA belongs to Zetex's legacy RF varactor family, engineered specifically for voltage-controlled oscillator stabilization in portable communications equipment operating from VHF through low-UHF bands.

FAQ

What is the maximum reverse voltage rating for each diode in ZDC833ATA?

The absolute maximum reverse breakdown voltage per diode is 25 V at I_R = 10 µA, verified per the January 1998 datasheet. Operation above 20 V is discouraged due to rising leakage and reduced capacitance linearity; design margin should maintain VR ≤ 20 V for reliable long-term VCXO performance.

Is ZDC833ATA RoHS-compliant and lead-free?

ZDC833ATA was manufactured prior to RoHS enforcement and uses standard SnPb terminations. Diodes Incorporated does not list a direct RoHS-compliant drop-in replacement; modern alternatives like the DVT1120 require circuit redesign due to differing C-V curves and package dimensions.

How does the 400 ppm/°C temperature coefficient impact VCXO stability?

The 400 ppm/°C tempco at 3 V means capacitance changes by 0.04% per °C, directly translating to frequency drift in crystal-pulling applications. When paired with a typical AT-cut crystal (−100 ppm/°C), this tempco enables partial compensation - reducing net drift to ~300 ppm/°C over −20°C to +70°C if uncorrected.

Can ZDC833ATA be used in series or parallel configurations?

Yes - pins 1 and 3 are independent anodes, allowing series (cathodes tied, anodes open) or parallel (anodes tied, cathode common) connection. Parallel use doubles effective capacitance but halves tuning range; series use halves capacitance while preserving ratio - both validated in Zetex app note AN-112 for multi-element VCXO topologies.