ST25R3910 datasheet(26/65 Pages) STMICROELECTRONICS

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Functional overview

ST25R3910

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ISO-14443 reader mode and in the NFCIP mode, where the ST25R3910 is the initiator. In

case of NFC target mode this sequence is started by receiving the interrogator request.

After the interrupt caused by the first initiator request command Unmask Receive Data is

sent to force the ST25R3910 in receive mode.

The commands Mask Receive Data and Unmask Receive Data are only accepted when the

receiver is enabled (bit rx_en is set).

AD Convert

A/D conversion of signal on AD_IN pin is performed; result is stored in A/D Output Register

(see Section 1.1.4 on page 8).

Duration time: 42 μs max.

This command is accepted in any mode where the oscillator and regulators are running.

Measure RF

This command measures the amplitude on the RFI inputs and stores result in the A/D

Output Register (see also Section 1.1.4 on page 8 and Section 1.1.3 on page 8).

When this command is executed the output of the Amplitude detector is multiplexed to the

A/D converter input (the A/D converter is in absolute mode). The Amplitude Detector

conversion gain is 0.6 Vinpp/Vout. One LSB of the A/D converter output represents

13.02 mVpp on the RFI inputs, a 3 Vpp signal (the maximum allowed level on each of the two

RFI inputs) results in 1.8 V output DC voltage and produces the value 1110 0110 on the A/D

converter output.

Duration time: 42 μs max.

This command is accepted in any mode where the oscillator and regulators are running.

Squelch

This direct command is intended to avoid demodulation problems of tags that produce a lot

of noise during data processing. It can also be used in a noisy environment. The operation

of this command is explained in Squelch.

Duration time: 500 μs max.

This command is only accepted when the transmitter and the receiver are operating.

Clear Squelch

Clears the gain reduction that was set by sending Squelch command.

This command is accepted in any mode.

Adjust Regulators

When this command is sent the power supply level of VDD is measured in maximum load

conditions and the regulated voltage reference is set 250 mV below this measured level to

ensure maximum possible stable regulated supply (see Section 1.2.8: Power supply,

Regulators). The use of this command increases the system PSSR.

At the beginning of execution of the command, both the receiver and transmitter are

switched on to have the maximum current consumption, and the regulators are set to their

maximum regulated voltage (5.1 V in case of 5 V supply and 3.4 V in case of 3.3 V supply).

After 300 μs VSP_RF is compared to VDD, if is not at least 250 mV lower the regulator setting

ST25R3910 Datasheet(PDF) 26 Page - STMicroelectronics

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