nrf53-series

nRF21540 RF FEM

The Nordic Thingy:53™ uses the nRF21540 RF FEM (U2) to improve the range and robustness of the connection on the nRF5340 System on Chip (SoC). The nRF21540 RF FEM enables RX gain up to +13 dB, low noise figure of 2.5 dB, and TX output power up to +21 dBm.

Note: The ANT2 port of nRF21540 RF FEM is terminated to 50 Ω as recommended in the nRF21540 RF FEM reference circuitry for single antenna. The ANT_SEL pin of the nRF21540 RF FEM is therefore connected to ground.

The nRF21540 RF FEM can be controlled through direct pin control or a built-in Serial Peripheral Interface (SPI) slave interface. You can select a predefined output level of +10 dBm or +20 dBm with direct pin control using the P0.12 General-Purpose Input/Output (GPIO) that is connected to the nRF21540 RF FEM MODE pin. To set an output power level that is not predefined you must use the SPI. For more information on the TX power control on the nRF21540 RF FEM, see TX power control in nRF21540 Product Specification.