STMicroelectronics BALFHB-WL-02D3

Overview

BALFHB-WL-02D3 from STMicroelectronics is an ultra-miniature integrated balun, matching network, and Tx harmonic filter optimized for QFN-packaged STM32WL sub-GHz wireless microcontrollers. It provides 50 Ω nominal input impedance conjugately matched to the STM32WL RFIO pins, delivers ≤0.85 dB Tx insertion loss at 915 MHz, achieves ≥26 dB harmonic attenuation at 2fo, and supports LoRa®, (G)FSK, (G)MSK, and BPSK modulations in LPWAN systems.

For engineers reviewing the BALFHB-WL-02D3 datasheet, BALFHB-WL-02D3 pinout, BALFHB-WL-02D3 application, or BALFHB-WL-02D3 equivalent, key selection criteria include its 862–928 MHz operating band, differential Rx balun with <±1.9° phase imbalance, integrated harmonics filtering up to 10fo, CSPG 8-bump package footprint, and compatibility with 4-layer QFN-4L PCB stack-ups requiring controlled-impedance RF routing.

Technical Context

This device implements ST's IPD (Integrated Passive Device) technology on a nonconductive glass substrate to deliver high RF performance in a 2.15 mm × 1.85 mm CSPG package. It integrates three functional blocks: a differential Rx balun (RFI_P_out/RFI_N_out), a single-ended Tx filter (RFO_in → RFO_out), and a shared ground architecture with three dedicated GND terminals (GND1–GND3).

The balun is specifically tuned for STM32WL's high-power mode RF interface: RFO_HP requires 57 Ω trace impedance, while RFI_out differential pair requires 61 Ω odd-mode (Zodd = 53 Ω) and 70 Ω even-mode (Zeven) routing. Antenna-side ports are strictly 50 Ω matched for both Tx and Rx paths, enabling direct connection to standard RF antennas without external matching.

Key Specifications

Pinout & Package

The BALFHB-WL-02D3 uses a CSPG (Chip Scale Package Glass) with 8 solder bumps in a 3×3 array (center pad omitted), measuring 2.15 mm × 1.85 mm and profile ≤630 µm after reflow. Ground terminals are distributed across three locations (GND1, GND2, GND3) to minimize RF return path inductance and suppress common-mode noise.

Key Features

Applications

Availability

BALFHB-WL-02D3 is available at Aetrix Electronics and suitable for smart utility meters, industrial sensor networks, and LPWAN asset tracking tags requiring stable component supply and full regulatory compliance support.

Supply support for BALFHB-WL-02D3 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, analog ICs, power management devices, and RF components for industrial, automotive, and IoT applications.

The BALFHB-WL-02D3 belongs to ST's IPD-based RF front-end portfolio, engineered specifically to simplify RF design for STM32WL wireless MCUs by integrating impedance matching, balancing, and harmonic filtering into a single miniature package.

FAQ

What is the recommended PCB stack-up for optimal BALFHB-WL-02D3 performance?

The validated stack-up uses a 4-layer board with 110–210 µm dielectric thickness between layer 1 (signal) and layer 2 (solid ground). Layer 1 must include a dedicated ground pour under the balun, connected via ≥8 vias within 1 mm of each GND bump. Trace impedances are fixed: RFO_out = 50 Ω, RFI_in = 50 Ω, RFO_HP = 57 Ω, and RFI_out differential = 61 Ω (Zodd = 53 Ω, Zeven = 70 Ω).

Can BALFHB-WL-02D3 be used with STM32WL in low-power mode?

No - the BALFHB-WL-02D3 is explicitly optimized for STM32WL high-power mode operation. Its impedance matching network targets the RFO_HP and RFI_out pins active only in high-power mode. In low-power mode, the STM32WL routes RF through different internal paths (RFO_LP and RFI_LP), which require the BALFHB-WL-02D1 variant.

Does this balun support both Tx and Rx paths simultaneously?

Yes - it integrates a bidirectional RF interface: the C3 pin serves as the single-ended antenna input for Rx, while C1 serves as the antenna output for Tx. The device operates in time-division duplex (TDD) mode synchronized with STM32WL's internal RF switch control, with no additional external switching required.

What is the maximum input power rating for continuous operation?

The absolute maximum RF input power is +27 dBm (500 mW) at ambient temperature of 25 °C. Derating is required above 25 °C: maximum power decreases linearly to +23 dBm at +105 °C. Exceeding this limit risks permanent damage to the IPD structure due to localized thermal stress in the glass substrate.