CRX14_10 Datasheet, PDF(9/47 Page) STMicroelectronics – ISO14443 type-B contactless coupler chip with anti-collision, CRC management and anti-clone function

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CRX14_10 Datasheet, PDF (9/47 Pages) STMicroelectronics – ISO14443 type-B contactless coupler chip with anti-collision, CRC management and anti-clone function

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CRX14

Signal description

See Figure 1: Logic diagram, and Table 1: Signal names, for an overview of the signals

connected to this device.

2.1

Oscillator (OSC1, OSC2)

The OSC1 and OSC2 pins are internally connected to the on-chip oscillator circuit. The

OSC1 pin is the input pin, the OSC2 is the output pin. For correct operation of the CRX14, it

is required to connect a 13.56MHz quartz crystal across OSC1 and OSC2. If an external

clock is used, it must be connected to OSC1 and OSC2 must be left open.

2.2

Antenna output driver (RFOUT)

The Antenna Output Driver pin, RFOUT, generates the modulated 13.56MHz signal on the

antenna. Care must be taken as it will not withstand a short-circuit.

RFOUT has to be connected to the antenna circuitry as shown in Figure 4: CRX14

application schematic The LRC antenna circuitry must be connected across the RFOUT pin

and GND.

2.3

Antenna input filter (RFIN)

The antenna input filter of the CRX14, RFIN, has to be connected to the external antenna

through an adapter circuit, as shown in Figure 4.

The input filter demodulates the signal generated on the antenna by the load variation of the

PICC. The resulting signal is then decoded by the 847kHz BPSK decoder.

2.4

Transmitter reference voltage (VREF)

The Transmitter Reference Voltage input, VREF, provides a reference voltage used by the

output driver for ASK modulation.

The Transmitter Reference Voltage input should be connected to an external capacitor, as

shown in Figure 4.

2.5

Serial clock (SCL)

The SCL input pin is used to strobe all IÂ²C data in and out of the CRX14. In applications

where this line is used by slave devices to synchronize the bus to a slower clock, the master

must have an open drain output, and a pull-up resistor must be connected from the Serial

Clock (SCL) to VCC. (Figure 5 indicates how the value of the pull-up resistor can be

calculated).

In most applications, though, this method of synchronization is not employed, and so the

pull-up resistor is not necessary, provided that the master has a push-pull (rather than open

drain) output.

Doc ID 8880 Rev 4

9/47

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