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ST25R3920 - NFC reader IC for digital car keys with a Noise Suppression Receiver (NSR)

ST25R3920 NFC Reader IC
ST25R3920 NFC Reader IC

STMicroelectronics has introduced the ST25R3920 as an extension to its portfolio of ST25R NFC reader ICs that is to be used in their digital car key line. The digital keys help the drivers to lock and unlock the cars using their smartphones and they can also enable new vehicle ownership models including car subscription services.


With a unique Dynamic Power Output (DPO) and a Noise suppression Receiver (NSR) technology, the device increases RF output power and offers an enhanced circuit design for rapid car key response and superior user convenience. With DPO, the new device can operate at up to 1.6W continuous RF output power and 2.5W short-term input peak to maintain reliable NFC connections over distance with a small antenna.


The NSR in the device helps to withstand interference from noise sources, hence it simplifies electromagnetic immunity and eases certification. The automatic antenna tuning compensates for the changes in the  RF environment for better connection to the user’s smartphone, whereas the flow power key-signal detection with inductive wakeup minimizes the load on the battery when the key is not in use.


The ST25R3920 is certified by the NFC Forum and it can work as an NFC reader or NFCuniversal device. It is compliant with the NFC Forum standards for pairing applications, as well as EMVCo 3.0 standards, hence they can be used as an in-car contactless-payment terminal for services such as electric-vehicle charging. The ST25R3920 is ideal for space-constrained locations that limit the maximum antenna size, it can be positioned in door handles, B-pillar, or center console.


Features of ST25R3920

  • Dynamic power output (DPO) controls the field strength to stay within given limits
  • Active waveshaping (AWS) reduces over and under-shoots
  • Noise suppression receiver (NSR) allows reception in a noisy environment
  • Automatic antenna tuning (AAT) via variable capacitor
  • Integrated EMVCo 3.0 compliant EMD handling
  • Automatic gain control and squelch feature to maximize SNR
  • Low power capacitive and inductive card detection
  • Low power NFC active and passive target modes
  • Adjustable ASK modulation depth, from 5 to 40%
  • Integrated regulators to boost system PSRR
  • 512-byte FIFO
  • Serial peripheral interface (SPI) up to 5 Mbit/s
  • I2C with up to 400 kbit/s in Fast-mode, 1 Mbit/s in Fast-mode Plus, and 3.4 Mbit/s in High-speed mode


Note: More technical information can be found in the datasheet linked at the bottom of this page and on the ST25B3920 product page

Component Datasheet

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