Broadcom Limited HSMS-2850-TR1

HSMS-2850-TR1 Schottky RF Detector Diode Product Summary

The HSMS-2850-TR1 from Broadcom Limited is part of the HSMS-285x family of zero-bias Schottky RF detector diodes, optimized for signal detection in small-signal applications at frequencies below 1.5 GHz. Packaged in the compact SOT-23-3 surface-mount format, this diode is designed for cost-effective, high-volume implementations primarily in RF/ID and RFID tag applications, especially in environments where low DC bias power is a critical design constraint. While the HSMS-2850-TR1 has obtained popularity for its high sensitivity at low signal levels (input power below –20 dBm), it is important to note that this model is classified as obsolete, necessitating special attention for ongoing designs and sourcing continuity.

Principal Characteristics and Packaging Types of the HSMS-2850-TR1

The HSMS-2850-TR1 is distinguished by its zero-bias operation and high detection sensitivity, making it ideal for energy-harvesting circuits or low-power receivers that cannot accommodate a primary bias supply. The diode exhibits low flicker noise (with a typical value of –162 dBV/Hz at 100 Hz), which is critical for applications requiring low-noise detection in the video frequency regime. The device’s miniature SOT-23-3 package supports automated assembly and compact PCB layouts—a valuable advantage for space-constrained RF or microwave board designs. The HSMS-285x series also includes other package variants such as SOT-143, SOT-323, and SOT-363 for broader design flexibility.

Broadcom employs precise wafer-level matching techniques in the HSMS-285x production process, ensuring that paired diodes within dual or multi-diode packages offer consistent characteristics, which simplifies matching for bridge or voltage doubler circuits. For designers aiming at high-reliability assemblies, the device offers a moisture sensitivity level (MSL) of 1, and a robust operating temperature range of –65°C to +150°C.

HSMS-2850-TR1 Electrical Properties and RF Performance Data

At the heart of the HSMS-2850-TR1’s appeal is its ability to deliver excellent RF detection at extremely low input powers. Key parameters for the single diode configuration include:

Maximum Forward Voltage (VF): 150 mV at 0.1 mA

Maximum Reverse Leakage Current (IR): 250 nA at a reverse voltage of 2 V

Junction Capacitance: 0.3 pF (@ 1V, 1 MHz)

Typical Tangential Sensitivity (TSS): –57 dBm at 915 MHz

Voltage Sensitivity: 40 mV/μW at 915 MHz

Video Resistance: 8 kΩ (zero bias, 915 MHz)

These characteristics enable the HSMS-2850-TR1 to deliver high sensitivity in RF detector circuits, supporting applications such as RF envelope detection, power measurement, and energy harvesting interfaces. The compact series resistance (Rs ≈ 25 Ω), low junction capacitance, and tailored video resistance facilitate efficient impedance matching and high signal-to-noise ratio in practical circuit designs. Performance curves such as forward current versus voltage and output voltage versus temperature are available to guide designers in predicting real-world behavior.

HSMS-2850-TR1 Maximum Ratings and Reliability Aspects

Robustness and reliability are paramount for any RF detector diode employed in field or industrial settings. The HSMS-2850-TR1 supports:

Peak Inverse Voltage (PIV): 2.0 V

Junction and Storage Temperature: –65°C to +150°C

Thermal Resistance: 500°C/W

Exceeding these ratings risks permanent damage or degraded performance. While the diode can tolerate standard production reflow and operating cycles, designers should observe careful ESD handling per referenced applications notes to prevent latch-up or early life failure. RoHS and REACH environmental status for this model should be confirmed if regulatory compliance is a sourcing or design imperative.

Circuit Integration and Application Examples for HSMS-2850-TR1

The HSMS-2850-TR1’s key design value lies in low-frequency equivalent circuit simplicity, described by a series resistance, junction resistance, and capacitance. For single-diode detector applications, its high sensitivity and low video impedance make it particularly suited to RFID tag receiving front ends and miniature power detectors. When higher voltage output is required, series or bridge configurations (using matched pairs such as the HSMS-2852 or HSMS-285C within the HSMS-285x family) allow voltage doubling or full-wave rectification, essential for certain low-bit-rate demodulator or energy harvesting circuits.

Engineers can exploit the device’s resistance and capacitance profile for precise impedance matching at 915 MHz or similar ISM band applications. Matching network design, using inductors and transmission lines as illustrated in datasheet examples, aids in maximizing power transfer and sensitivity across the intended frequency range. For protection against RF burnout in uncontrolled or high-power environments, employing a Schottky diode in conjunction with a suitable PIN limiter (e.g., HSMP-4820) may be appropriate.

Noise Performance and Assembly Recommendations for HSMS-2850-TR1

A critical parameter in low-level RF detection circuits is flicker noise, which is minimized in the HSMS-2850-TR1 through optimized junction and packaging technology. For designs operating at video frequencies below the flicker noise corner, the device offers significant advantages in receiver dynamic range and detection threshold. Detailed layout guidance—such as PCB pad recommendations for the SOT-23 and SOT-323 footprints—enables automated placement without degrading the RF or noise performance through added stray capacitance or inductance.

Alternative or Substitute Models for the HSMS-2850-TR1

Given the HSMS-2850-TR1’s obsolete status, engineers and sourcing teams should consider direct replacements or alternatives within the Broadcom HSMS-285x family where possible. Notable equivalents include:

HSMS-285B: SOT-323 single diode configuration

HSMS-2852 and HSMS-285C: Series pair/double-diode options for voltage doubling

HSMS-282x (for higher power, up to 4 GHz, if the application requires greater input levels)

HSMS-286x (for frequencies above 4 GHz requiring zero bias diodes)

The selection must be guided by matching electrical and package characteristics to ensure compatibility with existing designs. Always reference the latest manufacturer reliability, compliance, and performance tables when making substitution decisions.

Conclusion

The HSMS-2850-TR1, representing Broadcom Limited’s commitment to high-performance, low-noise Schottky RF detector diodes for zero-bias applications, is ideally suited for RFID and RF/ID detection designs below 1.5 GHz. While its role in legacy designs is well established due to its sensitivity, low noise, and convenient package, its obsolescence requires careful consideration for continuity in new designs. With an array of related models available, engineers can retain core design attributes by leveraging the broader HSMS-285x or adjacent Schottky series solutions, assured by comprehensive electrical, RF, and application data that facilitates informed component selection and robust circuit implementation.