NXP Semiconductors BB172X

Overview

BB172X from NXP Semiconductors is a VHF variable capacitance diode (varactor) fabricated in planar technology and housed in an SOD323 (SC-76) surface-mount package. It delivers Cd(1V) = 34.65–42.35 pF, Cd(28V) = 2.361–2.754 pF, Cd(1V)/Cd(28V) ratio ≥13.5, rs = 0.65–0.8 Ω at 100 MHz, and supports reverse voltage up to 32 V. It is engineered for tuning circuits in high-frequency oscillator designs.

For engineers reviewing the BB172X datasheet, BB172X pinout, BB172X application, or BB172X equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, and two confirmed alternative varactors with documented parameter differences for VCO tuning applications.

Technical Context

The BB172X operates as a reverse-biased junction capacitor whose depletion width-and thus capacitance-varies nonlinearly with applied DC bias. Its planar construction ensures stable C-V characteristics across 1–28 V, with typical Cd(1V)/Cd(28V) = 15 and low series resistance (rs ≤ 0.8 Ω) critical for minimizing Q-factor degradation in VHF resonant tanks.

Designed specifically for voltage-controlled oscillators, it exhibits a diode capacitance temperature coefficient that remains within ±200 ppm/°C over its operating range and maintains IR ≤ 10 nA at VR = 30 V and 25 °C-enabling low-phase-noise tuning in compact RF modules.

Key Specifications

Pinout & Package

The BB172X is supplied in the SOD323 (SC-76) plastic surface-mounted package: 2-terminal, ultra-compact footprint (1.7 × 1.25 × 0.95 mm), cathode-marked with a bar on the top surface.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BB172X, BBY52-02W offers lower baseline capacitance but reduced tuning ratio and higher loss, while MV2103 trades 4 V VR headroom and 1.0 pF lower Cd(1V) for marginally higher rs-making BB172X optimal for wide-span, low-phase-noise VHF VCOs demanding both high ratio and low loss.

Availability

BB172X is available at Aetrix Electronics and suitable for voltage-controlled oscillators, FM modulators, RF filter tuning, and PLL reference divider circuits requiring stable component supply, consistent C-V performance, and SOD323 footprint compatibility.

Supply support for BB172X 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

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The BB172X belongs to NXP's RF discrete portfolio, designed specifically for high-linearity, low-loss VHF tuning in compact wireless transceivers and frequency-agile communication systems.

FAQ

What is the primary function of the BB172X in RF circuits?

The BB172X functions as a voltage-controlled variable capacitance diode (varactor), used to tune resonant frequency in VHF oscillator and filter circuits. Its capacitance changes with applied reverse bias-ranging from 34.65 pF at 1 V to 2.361 pF at 28 V-enabling precise electronic frequency control without mechanical adjustment. This behavior makes the BB172X essential in VCOs, FM modulators, and tunable matching networks where analog voltage tuning is required.

Does the BB172X have a specified maximum junction temperature?

Yes, the BB172X has a maximum junction temperature (Tj) of +125 °C, as defined in Table 5 of its NXP datasheet. This rating ensures reliable operation under sustained RF power dissipation and ambient thermal conditions typical in densely packed RF front-ends. The device also supports storage temperatures from −55 °C to +150 °C, confirming robustness across industrial environmental profiles. Thermal design for BB172X should maintain Tj ≤ +125 °C using standard PCB copper pour practices.

How is the cathode identified on the BB172X package?

The cathode of the BB172X is identified by a marking bar on the top surface of the SOD323 (SC-76) package, per Figure 4 and Pinning section in the NXP datasheet. Pin 1 is the cathode and Pin 2 is the anode. This marking aligns with industry-standard polarity identification for surface-mount varactors and must be observed during PCB layout to ensure correct reverse-bias connection-critical for proper capacitance tuning and avoiding forward conduction.

What is the typical series resistance (rs) of the BB172X and why does it matter?

The BB172X has a typical series resistance (rs) of 0.65 Ω at 100 MHz and Cd = 30 pF, with a maximum of 0.8 Ω. This low rs value directly impacts the quality factor (Q) of resonant LC tanks: Q = 1/(2πf·rs·C). At 150 MHz and 10 pF, rs = 0.65 Ω yields Q ≈ 164-minimizing phase noise and sustaining stable oscillation. Higher rs would degrade Q, increase close-in phase noise, and reduce tuning efficiency-making rs a critical selection parameter for VHF VCO designs.

Can the BB172X be used in automotive applications?

No, the BB172X is not automotive-qualified. Per NXP's legal disclaimers (Section 10.3), unless explicitly stated as automotive qualified in the datasheet-which it is not-the BB172X is not tested or warranted for automotive use. It lacks AEC-Q200 stress qualification, extended temperature validation beyond +125 °C junction, or failure-in-time (FIT) data required for automotive ECUs. For automotive VCOs, designers must select components explicitly rated and certified for automotive grade, such as AEC-Q200 varactors from qualified NXP automotive portfolios.