ST25R3916 datasheet(64/157 Pages) STMICROELECTRONICS

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Application information

ST25R3916/7

64/157

DS12484 Rev 4

4.4.8

Measure amplitude

This command measures the amplitude of the RF signal on the RFI inputs and stores the

result in the A/D converter output register.

This command enables the transmitter and amplitude detector. The transmitter drives the

antenna, and the amplitude detector converts the differential RF signal received back

between RFI1 and RFI2 into a proportional DC voltage. This DC voltage is converted with

the A/D converter in absolute conversion mode into an 8-bit value and stored in the A/D

converter output register.

The amplitude detector conversion gain is 0.6 VinPP / Vout referenced to the RF signal on a

single RFI pin. Thus, one LSB of the A/D converter output represents 13.02 mVPP on either

of the RFI inputs.

Note:

The maximum allowed voltage level on an RFI pin is 3 VPP. This results in 1.8 V output DC

voltage of the amplitude detector and produces a value of E6h after A/D conversion.

Duration time: 25 μs max.

4.4.9

Reset RX gain

This command initializes the AGC, Squelch and RSSI block and resets the gain reduction to

the value set in Receiver configuration register 4. Sending this command also stops any

ongoing squelch process.

4.4.10

Adjust regulators

When this command is sent, then the transmitter and receiver are enabled to ensure a high

current draw and the regulated voltage VDD_RF is set 250 mV below the power supply level

of VDD_TX. Before sending the adjust regulator command it is required to toggle the bit reg_s

by setting it first to 1 and then reset it to 0. After the adjustment is completed the state of the

transmitter and receiver prior to the command execution is restored (either enabled or

disabled).

Duration time: 5 ms max.

This command is not accepted if external definition of the regulated voltage is selected in

the Regulator voltage control register (bit reg_s is set to 1).

4.4.11

Measure phase

This command measures the phase difference between the signals on the RFO outputs and

the signals on the RFI inputs and stores the result in the A/D converter output register.

This command enables the transmitter and phase detector, and performs an A/D conversion

of the output of the phase detector with the A/D converter in relative mode. The phase

measurement results can be calculated using the following formulas:



0 ≤ Φ ≤ 17º: result = 255



17 < Φ < 163º: angle [º] = 17 + (1 -result / 255) * 146



163 ≥ Φ ≥ 180º: result = 0

Duration time: 25 μs max.

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