CRX14_05 Datasheet, PDF (7/40 Pages) STMicroelectronics – Low Cost ISO14443 type-B Contactless Coupler Chip with Anti-Collision, CRC Management and Anti-Clone Function

CRX14
SIGNAL DESCRIPTION
See Figure 2., and Table 1., for an overview of the
signals connected to this device.
Oscillator (OSC1, OSC2). The OSC1 and OSC2
pins are internally connected to the on-chip oscil-
lator 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 exter-
nal clock is used, it must be connected to OSC1
and OSC2 must be left open.
Antenna Output Driver (RF_OUT). The Antenna
Output Driver pin, RF_OUT, generates the modulat-
ed 13.56MHz signal on the antenna. Care must be
taken as it will not withstand a short-circuit.
RF_OUT has to be connected to the antenna circuit-
ry as shown in Figure 5. The LRC antenna circuitry
must be connected across the RF_OUT pin and
GND.
Antenna Input Filter (RF_IN). The antenna input
filter of the CRX14, RF_IN, has to be connected to
the external antenna through an adapter circuit, as
shown in Figure 5.
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.
Transmitter Reference Voltage (V_REF). The
Transmitter Reference Voltage input, V_REF, pro-
vides 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 5.
Serial Clock (SCL). The SCL input pin is used to
strobe all I²C data in and out of the CRX14. In ap-
plications where this line is used by slave devices
to synchronize the bus to a slower clock, the mas-
ter must have an open drain output, and a pull-up
resistor must be connected from the Serial Clock
(SCL) to V_CC. ( Figure 6. indicates how the value
of the pull-up resistor can be calculated).
In most applications, though, this method of syn-
chronization 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.
Serial Data (SDA). The SDA signal is bi-direc-
tional. It is used to transfer I²C data in and out of
the CRX14. It is an open drain output that may be
wire-OR’ed with other open drain or open collector
signals on the bus. A pull-up resistor must be con-
nected from Serial data (SDA) to V_CC. (Figure 6.
indicates how the value of the pull-up resistor can
be calculated).
Chip Enable (E0, E1, E2). The Chip Enable in-
puts E0, E1, E2 are used to set and reset the value
on the three least significant bits (b3, b2, b1) of the
7-bit I²C Device Select Code. They are used for
hardwired addressing, allowing up to eight CRX14
devices to be addressed on the same I²C bus.
These inputs may be driven dynamically or tied to
V_CC or GND to establish the Device Select Code
(note that the V_IL and V_IH levels for the inputs are
CMOS compatible, not TTL compatible).
When left open, E0, E1 and E2 are internally read
at the logic level 0 due to the internal pull-down re-
sistors connected to each inputs.
Power Supply (V_CC, GND, GND_RF). Power is
supplied to the CRX14 using the V_CC, GND and
GND_RF pins.
V_CC is the Power Supply pin that supplies the pow-
er (+5V) for all CRX14 operations.
The GND and GND_RF pins are ground connec-
tions. They must be connected together.
Decoupling capacitors should be connected be-
tween the V_CC Supply Voltage pin, the GND
Ground pin and the GND_REF Ground pin to filter
the power line, as shown in Figure 5.
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