ST25DV04K datasheet(72/197 Pages) STMICROELECTRONICS

72 / 197 page

RF operation

Contactless exchanges are performed in RF mode as specified by ISO/IEC 15693 or NFC Forum Type 5.

The ST25DVxxx communicate via the 13.56 MHz carrier electromagnetic wave, on which incoming data are

demodulated from the received signal amplitude modulation (ASK: amplitude shift keying). The received ASK

wave is 10% or 100% modulated, with a data rate of 1.6 Kbit/s using the 1/256 pulse coding mode, or a data rate

of 26 Kbit/s using the 1/4 pulse coding mode.

Outgoing data are generated by the ST25DVxxx load variation using Manchester coding with one or two

subcarrier frequencies at 423 and 484 kHz. Data are transferred from the ST25DVxxx at 6.6 Kbit/s in low data

rate mode, at 26 Kbit/s in high data rate mode. The ST25DVxxx supports 53 Kbit/s in high data rate mode in one

subcarrier frequency at 423 kHz.

The ST25DVxxx follows ISO/IEC 15693 or NFC Forum Type 5 recommendations for radio-frequency power and

signal interface and for anticollision and transmission protocol.

7.1

RF communication

7.1.1

Access to an ISO/IEC 15693 device

The dialog between the “RF reader” and the ST25DVxxx takes place as follows:

•

device activation by the RF operating field of the reader

•

transmission of a command by the reader (the device detects carrier amplitude modulation)

•

transmission of a response by the device using load modulation

These operations use the RF power transfer and communication signal interface described below. This technique

is called RTF (Reader talk first).

Operating field

The ST25DVxxx operates continuously between the minimum and maximum values of the electromagnetic field H

defined in Table 253. RF characteristics. The reader must generate a field within these limits.

Power transfer

Power is transferred to the ST25DVxxx by radio frequency at 13.56 MHz via coupling antennas. The RF

operating field of the reader is transformed on the device antenna into an AC voltage, which is rectified,

filtered and internally regulated. During communication, the amplitude modulation (ASK) on this received signal is

demodulated by the ASK demodulator

Frequency

The ISO 15693 standard defines the carrier frequency (fC) of the operating field as 13.56 MHz ±7 kHz.

7.2

RF communication and energy harvesting

As the current consumption can affect the AC signal delivered by the antenna, RF communications with

ST25DVxxx are not guaranteed during voltage delivery on the energy harvesting analog output V_EH.

RF communication can disturb and possibly stop Energy Harvesting mode.

7.3

Fast transfer mode mailbox access in RF

Thanks to dedicated commands, the RF interface has the possibility to check Mailbox availability, and the

capability to access it directly to put or get a message from it (see Section 5.1 Fast transfer mode (FTM) for

specific features).

ST25DV04K ST25DV16K ST25DV64K

RF operation

DS10925 - Rev 11

page 72/197

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