AS3911 Datasheet, PDF (137/149 Pages) ams AG – NFC Initiator / HF Reader IC

Application Information
Figure 123:
Connection of Tuning Capacitors to the Antenna LC Tank in case of Single (left) and Differential
Driving (right)
TRIM1_0
TRIM1_1
TRIM1_2
TRIM1_3
RF01
RF02
RFI1
RFI2
TRIM2_3
TRIM2_2
TRIM2_1
TRIM2_0
Antenna
TRIM1_0
TRIM1_1
TRIM1_2
TRIM1_3
RF01
RF02
RFI1
RFI2
TRIM2_3
TRIM2_2
TRIM2_1
TRIM2_0
½ Antenna
½ Antenna
Antenna Tuning Using ‘Antenna Calibration Control’ Register
There is also a possibility to control the position of the TRIM
switches by writing the Antenna Calibration Control Register.
When the bit trim_s of this register is set to 1 position of the
trim switches is controlled by bits tre_3 to tre_0.
Using this register and performing phase and amplitude
measurements (using direct commands Measure Phase and
Measure Amplitude) different tuning algorithms can be
implemented in the external controller.
Stream Mode and Transparent Mode
Standard and custom 13.56 MHz RFID reader protocols, which
are not supported by the AS3911 framing, can be realized using
the AS3911 AFE and framing implemented in the external
microcontroller.
Transparent Mode
After sending the direct command Transparent Mode the
external microcontroller directly controls the transmission
modulator and gets the Receiver output (control logic becomes
“transparent”).
ams Datasheet, Confidential: 2013-Oct [2-03]
AS3911 – 137