Passive Z

STMicroelectronics has released nine chip-scale passive RF balun ICs that include antenna impedance-matching and harmonic filtering for its STM32WL sub0GHz wireless microcontrollers.

Intended to sit in Rx and TX paths between the MCUs and their antennas, the 8bump parts are in 2.13 x 1.83mm packages with a maximum height of 630µm after reflow.

Applications are foreseen in LoRaWAN, Sigfox, M-Bus wireless and Mioty networks.

"By integrating all the components on one die, they ensure consistent performance by avoiding the process variations that affect conventional matching networks built with discrete components," the company said.

The variants let designers choose parameters according to the frequency range, power, MCU package type, and PCB layer count – either two or four-layer.

Taking the BALFHB-WL-01D3 as an example, it has 50Ω nominal antenna ports, and a balun matched to BGA-packaged MCUs on four-layer boards. Operation is over 862 – 928MHz and with LoRa, (G)FSK, (G)MSK or BPSK modulation.

The BALFHB-WL-01D3 data sheet is here, and there is a general web page.

The MCUs have an Arm Cortex-M4 application processor and a Cortex-M0+ core to manage the on-chip radios. LoRaWAN and Sigfox stacks are included in the STM32CubeWL MCU software package.