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New Integrated Filter Matched Balun’s for STM32WL Microcontrollers

New antenna matching balun’s are designed for maximizing RF performance for a number of different wireless networks

STMicroelectronics have released a number of new RF integrated passive devices (RF IPDs) that combine antenna impedance-matching, balun, and harmonic-filter circuity, which are optimized for use with STM32WL wireless microcontrollers (MCUs).

New Integrated Filter Matched Balun for STM32WL Microcontrollers

The RF IPDs, packaged as tiny chip-scale devices, connect the STM32WL MCU to its antenna and help maximize the RF performance. By integrating all the components on one die, this ensures consistent performance avoiding the process variations that affect conventional matching networks that are built with discrete components. They also simplify circuit design, save on the number of parts required, and permit a smaller form factor, making them ideal for cost-sensitive and space-constrained IoT devices.

The nine RF IPD variants available let designers choose the optimum parameters according to the RF frequency range and power, MCU package type, and two- or four-layer PCB. The STMicroelectronics series comprise the BALFHB-WL-01D3 through BALFHB-WL-06D3 for applications at 868MHz and 915MHz frequencies. The BALFLB-WL-07D3, BALFLB-WL-08D3, and BALFLB-WL-09D3 which are optimized for operation at 490MHz. Each integrates the complete receive and transmit signal paths between the MCU and antenna. The integrated filter provides high attenuation of unwanted transmitter harmonics, helping designers satisfy the regulations set by various radio-licensing authorities worldwide.

STMicroelectronics STM32WL MCUs combine application-level processing and wireless communication for smart, connected devices, by integrating an Arm® Cortex®-M4 MCU with a sub-GHz long-range radio managed by a separate Cortex-M0+ core. The radio is LPWAN compliant, supports multiple modulation schemes, and comes with LoRaWAN® and Sigfox™ stacks included in the STM32CubeWL MCU software package.

Features of STM32WL Integrated Filter Matched Balun's include:

  • STM32WL sub-GHz wireless microcontrollers impedance matched balun and Tx harmonics filter
  • Optimized versions for both BGA and QFN STM32WL sub-GHz wireless microcontrollers in high power mode and dedicated to 2-layer and 4-layer PCB's
  • 50 Ω nominal input / conjugate matched balun to BGA and QFN STM32WL
  • 50 Ω nominal impedance on antenna side Tx and Rx
  • Deep Tx rejection harmonic filter
  • Low insertion loss
  • Small footprint
  • Low profile ≤ 630µm after reflow
  • High RF performance

More information on the STM32WL Filter Matched Balun's is available on the ST website at STMicroelectronics RF Front-end main page.

The STMicroelectronics website address is www.st.com
[Reprinted with kind permission from STMicroelectronics - Release Date, 16th February, 2023]