Diodes Incorporated ZMV931TA

Overview

ZMV931TA from Zetex Semiconductors is a 12 V hyperabrupt silicon varactor diode in SOT-23 package, designed for voltage-controlled oscillator (VCO) and temperature-compensated crystal oscillator (TCXO) tuning circuits. 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 wireless transceivers.

For engineers reviewing the ZMV931TA datasheet, ZMV931TA pinout, ZMV931TA application, or ZMV931TA equivalent, key selection criteria include its octave-tuning range (0–6 V), hyperabrupt C-V slope for linear frequency modulation, low IR for minimal oscillator drift, and SOT-23 footprint compatibility with high-density RF layouts.

Technical Context

This varactor operates as a voltage-dependent capacitor in resonant tank circuits, where applied reverse bias modulates junction depletion width to shift oscillation frequency. Its hyperabrupt doping profile yields a C ∝ V^−γ relationship (γ ≈ 2.5–3.0), supporting wide, monotonic tuning across 0–6 V without capacitance discontinuities.

Specified at 25°C, it maintains stable C-V tracking across temperature (±300–400 ppm/°C coefficient) and exhibits <100 nA leakage at 8 V, ensuring minimal DC loading on bias networks and preserving Q-factor integrity in 50–200 MHz VCO designs.

Key Specifications

Pinout & Package

Package: SOT-23 (JEDEC TO-236AB), 3-pin surface-mount plastic case, 2.67–3.05 mm length, 1.20–1.40 mm width, 0.91–1.16 mm height. Cathode marked by molded notch or bar.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMV1232-011LF and BBY58-02W, ZMV931TA uniquely balances 13.5 pF starting capacitance, 300 Q, and SOT-23 compatibility - making it optimal for mid-range VCOs where both tuning depth and spectral purity must coexist in compact form factors.

Availability

ZMV931TA is available at Aetrix Electronics and suitable for VCXO design, TCXO compensation networks, mobile radio VCOs, and pager IF filters requiring stable component supply with tight C-V matching and low-phase-noise performance.

Supply support for ZMV931TA 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 Diodes Incorporated) specialized in high-performance analog and RF discrete semiconductors, with focus on low-noise, high-Q, and precision-tolerance devices for timing and signal conditioning.

The ZMV931TA belongs to Zetex's hyperabrupt varactor family engineered specifically for voltage-controlled frequency synthesis in wireless infrastructure and portable communications equipment.

FAQ

What is the recommended PCB pad layout for ZMV931TA in RF-sensitive applications?

Use symmetric, non-soldermask-defined pads per JEDEC MO-203-AB (SOT-23): 0.9 mm × 1.1 mm for pins 1 and 2, 0.9 mm × 0.6 mm for pin 3. Ground plane must fully surround the cathode pad; keep anode trace <2 mm long and 0.25 mm wide with 50 Ω impedance control. Avoid vias under the device body.

Can ZMV931TA be used in series-tuned VCO configurations?

Yes - its hyperabrupt profile and low series resistance (derived from Q ≥ 300 at 50 MHz) support stable operation in series-resonant tanks. However, ensure DC blocking capacitors ≥100 pF are placed between varactor and active device to prevent forward conduction during large-signal swing.

How does temperature affect ZMV931TA's capacitance tuning linearity?

Capacitance vs. voltage remains monotonic across −40°C to +125°C, but the C-V slope shifts: at 85°C, C_1V increases ~8% and C_4V increases ~6% versus 25°C. The +350 ppm/°C tempco applies only to small-signal ΔC/ΔT at fixed bias - not to overall tuning curvature.

Is ZMV931TA RoHS-compliant and halogen-free?

Yes - manufactured per Diodes Incorporated's standard RoHS-6 and halogen-free specifications (IEC 61249-2-21). The SOT-23 molding compound meets IPC/JEDEC J-STD-020D moisture sensitivity level 1, with peak reflow temperature up to 260°C.