AS3911 datasheet(16/159 Pages) AMSCO

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[v2-11] 2016-Jun-13

AS3911 − Detailed Description

One regulator is for the analog blocks, one for digital blocks,

there is also a separate one for the antenna drivers. In case of

low cost applications some (or all) regulators may not be used

to save on external components.

This block additionally generates a reference voltage for the

analog processing (AGD - analog ground). This voltage also has

an associated external buffer capacitor.

POR and Bias

This block contains the bias current and voltage generator

which provides bias currents and reference voltages to all other

blocks. It also incorporates a Power on Reset (POR) circuit which

provides a reset at power-up and at low supply levels.

RC Oscillator and Wake-up Timer

The AS3911 includes several possibilities of low power

detection of a card presence (capacitive sensor, phase

measurement, amplitude measurement). RC oscillator and

periodic detection. When presence of a card is detected an

interrupt is sent to controller.

ISO14443 and NFCIP-1 Framing

This block performs framing for receive and transmit according

to the selected ISO mode and bit rate settings.

In reception it takes demodulated sub-carrier signal from

Receiver. It recognizes the SOF, EOF and data bits, performs

parity and CRC check, organizes the received data in bytes and

places them in the FIFO.

During transmit, it operates inversely, it takes bytes from FIFO,

generates parity and CRC bits, adds SOF and EOF and performs

final encoding before passing modulation signal to transmitter.

In Transparent mode, the framing and FIFO are bypassed, the

digitized sub-carrier signal, which is Receiver output, is directly

sent to MISO pin, signal applied to MOSI pin is directly used to

modulate the transmitter.

FIFO

The AS3911 contains a 96 byte FIFO. Depending on the mode,

it contains either data which has been received or data which

is to be transmitted.

Control Logic

The control logic contains I/O registers which define operation

of device.

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