nRF21540 RF Front End Module – a ‘plug and play’ range extender for its short-range wireless portfolio

Written by Mike Benson

January 13, 2020

The nRF21540 RF Front End Module is a range extender optimized to boost the link budget of Nordic’s nRF52 and nRF53 Series advanced multiprotocol wireless SoCs. When combined with an nRF52 Series SoC, the nRF21540 RF FEM’s +21 dBm TX output power and 13 dB RX gain ensure a superior link budget for up to 16x range extension

Nordic Semiconductor recently announced the nRF21540TM RF Front End Module (FEM), its first power amplifier/low noise amplifier (PA/LNA) product. The nRF21540 has been developed to perfectly complement Nordic’s nRF52 and nRF53 Series multiprotocol Systems-on-Chip (SoCs). The RF FEM’s PA offers a highly adjustable TX power boost up to +21 dBm, with the LNA providing +13 dB RX gain. The LNA’s low noise figure (NF) of only 2.5 dB also ensures increased RX sensitivity for Nordic’s Bluetooth® 5/Bluetooth Low Energy (Bluetooth LE), Thread, Zigbee, and 2.4GHz RF low power wireless solutions. When combined with an nRF52840 SoC running Bluetooth LE at 1 Mbps, for example, the nRF21540 improves the RX sensitivity by 5 dBm. Coupled with the increased output power, the connection link budget is raised by 18 dBm. For other devices with less than +8 dBm TX power on-chip, the improvements are even larger. The resulting increase in connection link budget offers significantly longer range and helps lower the number of retransmissions due to corrupt packages. The nRF21540 is a valuable addition for all applications that may require increased range or robust coverage. Some example applications are asset tracking, audio, smart home, or industrial use cases.

The nRF21540 is a ‘plug and play’ complementary device when used with Nordic’s short-range wireless SoCs. The nRF21540 connects to the SoC’s antenna output and features two additional antenna ports to enable antenna diversity features. The device’s gain control, antenna switching, and power modes are controlled via GPIO or SPI or a combination of both. While the device can be used with other radios, the ease of use with Nordic SoCs is further enhanced as driver support will be rolled out as part of future releases of Nordic’s nRF5 SDK, nRF5 SDK for Thread and Zigbee, and the nRF Connect SDK.
The nRF21540’s TX power is dynamically adjustable and output power can be set up to 21 dBm in small increments. This ensures designs can run with output power within 1 dBm of the allowable range across all regions and operating conditions. During use the power setting can be dynamically controlled by the SoC to take into account the requirements of the current connection. For example, received signal strength indication (RSSI) and other parameters can be monitored to determine power requirements for a particular connection and TX power raised or lowered to manage power consumption. Any variations due to temperature can be counteracted so the output power is stable at the desired level.
Operating across a 1.7 to 3.6 V supply range, the nRF21540 offers competitive power numbers of 115 mA at TX tuned to +20 dBm, 4.1 mA in RX mode, and 30 nA in power down mode. The device is qualified across a -40 to 105°C range allowing it to complement Nordic’s high-temperature rated nRF52833 and nRF5340 in applications such as professional lighting. The chip is supplied in a 4×4 mm QFN16 package, and complementing the release of the nRF21540 IC itself, Nordic offers development boards that enable evaluation of the RF FEM performance using lab equipment, as well as real application performance combined with an nRF52 Series device.
“Many applications benefit from the significant range boost offered by an external RF Front End Module,” says Kjetil Holstad, Director of Product Management at Nordic Semiconductor. “But it’s important the FEM doesn’t compromise other features of the radio’s performance or has significant impact on battery life. With Nordic’s decades of experience in low power wireless design, our engineering team has designed a competitive RF FEM that is optimized for, and perfectly complements, the company’s advanced multiprotocol SoCs at a size and price that minimizes impact on the BOM and board real estate.”
The nRF21540 RF FEM is now sampling to lead customers. For further information reach out to Nordic’s sales organization.


  • Supports Bluetooth® Low Energy, 802.15.4, and proprietary applications
  • Max output power 22 dBm
  • Adjustable output power to ±1 dB from 5 to 21 dBm
  • User programmable modes for TX gain
  • Support for two antenna interfaces
  • Receive gain +13 dB
  • Single-ended 50 Ω matched input and output
  • 115 mA @ +20 dBm output power
  • 42 mA @ +10 dBm output power
  • Control interface via IO, SPI, or a combination of both
  • Supply voltage 1.7 to 3.6 V, suitable for 1.8+/-5% systems
  • Operating temperature -40°C to 105°C
  • Package variant QFN16 4 x 4 mm


            • Smart Home applications
            • Industrial and factory automation
            • Asset tracking
            • Advanced CE remote controls
            • Sports and Fitness
            • Toys
            • Medical
            • Beacons

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