Infineon Technologies BB 689 E7908

Overview

BB689 E7908 from Infineon Technologies is a silicon tuning diode (varactor) designed for VHF TV tuner front-end voltage-controlled oscillator (VCO) and RF filter tuning circuits. It delivers a capacitance range of 2.5–61.5 pF at 1 MHz, 18–23.2:1 capacitance ratio (VR = 1 V / 28 V), and low series resistance of 0.85 Ω (typ.) at 470 MHz - enabling high-Q resonant tank performance in compact analog tuners.

For engineers reviewing the BB689 E7908 datasheet, BB689 E7908 pinout, BB689 E7908 application, or BB689 E7908 equivalent, key selection criteria include its SC79 package footprint, 30 V reverse voltage rating, ±2% capacitance matching across matched diode sequences, temperature coefficient of capacitance (TCC), and RoHS-compliant Pb-free construction for legacy broadcast receiver designs.

Technical Context

This varactor operates as a voltage-dependent capacitor where reverse bias controls junction depletion width. Its capacitance vs. voltage (C–V) curve is specified from 1–28 V at 1 MHz, with monotonic decrease from 51 pF to 2.5 pF (typ.). The 0.6 nH series inductance and sub-1.2 Ω r_S support stable RF impedance up to VHF bands without parasitic resonance.

Manufactured using Infineon's "in-line" matching assembly, the BB689 achieves ≤2% ∆C/C matching across 7-diode sequences - critical for multi-stage filter alignment in analog TV tuner modules. Its −55 °C to +150 °C operating range supports under-chassis mounting in thermally demanding tuner cans.

Key Specifications

Pinout & Package

BB689 E7908 is housed in an SC79 plastic surface-mount package (JEDEC TO-236AB variant), measuring 1.3 mm × 0.7 mm × 0.5 mm with gull-wing leads. Cathode is marked by a laser-etched bar on the top surface. The device has two terminals only: anode and cathode.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BB669 E7908, BB689 E7908 offers wider tuning range and tighter matching - critical for multi-standard VHF receivers; versus BB689-02V E7908, it shares identical RF performance but requires different reel logistics planning.

Availability

BB689 E7908 is available at Aetrix Electronics and suitable for VHF TV tuner modules, FM radio synthesizers, legacy CATV descramblers, and RF calibration equipment requiring stable component supply and long-lifecycle support.

Supply support for BB689 E7908 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

Infineon Technologies AG is a German semiconductor manufacturer specializing in power management, automotive, industrial, and RF components, with global R&D and fabrication facilities.

The BB689 belongs to Infineon's legacy silicon tuning diode product line, engineered specifically for analog broadcast receiver systems requiring high-C-ratio, low-r_S, and batch-matched varactors before digital tuner dominance.

FAQ

What is the maximum recommended reverse voltage for continuous operation?

The BB689 E7908 is rated for 30 V DC reverse voltage at 25 °C ambient. At elevated temperatures (e.g., 85 °C), derating is not specified in the datasheet, but sustained operation above 28 V is discouraged due to increased leakage and accelerated aging. Peak transient voltage must not exceed 35 V, even briefly.

Does BB689 E7908 require external biasing circuitry for RF applications?

Yes - a DC blocking capacitor (e.g., 100 pF NP0) must isolate the tuning voltage from the RF path, and a high-value RF choke (≥1 kΩ at operating frequency) must supply bias while preventing RF leakage. No internal bias network is integrated; the diode operates strictly as a two-terminal passive varactor.

How does temperature affect capacitance stability in BB689 E7908?

Capacitance exhibits a negative temperature coefficient (TCC), ranging from −5×10⁻⁴/°C to −1×10⁻³/°C depending on bias voltage. At VR = 1 V, TCC ≈ −3.5×10⁻⁴/°C; at VR = 28 V, it shifts to −7.2×10⁻⁴/°C. This must be compensated in high-stability VCO designs via NTC thermistors or lookup-table correction.

Can BB689 E7908 be substituted with a GaAs varactor in the same footprint?

No - GaAs varactors (e.g., M/A-COM MA46H120) have different C–V curves, higher r_S (>2 Ω), and incompatible thermal expansion. The SC79 footprint is mechanically compatible, but electrical mismatch causes >15% frequency drift and degraded Q. Direct substitution is not validated or recommended.