CR14 STMicroelectronics, CR14 Datasheet - Page 9

• Manufacturer Part Number: CR14
• Description: Low Cost Iso14443 Type-b Contactless Coupler Chip With Anti-collision And Crc Management
• Manufacturer: STMicroelectronics

CR14
2
2.1
2.2
2.3
2.4
2.5
Signal description
See
connected to this device.
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 CR14, 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.
Antenna Output Driver (RF
The Antenna Output Driver pin, RF
antenna. Care must be taken as it will not withstand a short-circuit.
RF
Schematic
Antenna Input Filter (RF
The antenna input filter of the CR14, RF
an adapter circuit, as shown in
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
The Transmitter Reference Voltage input, V
driver for ASK modulation.
The Transmitter Reference Voltage input should be connected to an external capacitor, as
shown in
Serial Clock (SCL)
The SCL input pin is used to strobe all I²C data in and out of the CR14. 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 V
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.
OUT
Figure 1: Logic
has to be connected to the antenna circuitry as shown in
Figure
CC
The LRC antenna circuitry must be connected across the RF
.
(Figure 5
4.
Diagram, and
indicates how the value of the pull-up resistor can be calculated).
Figure
Table 1: Signal
OUT
IN
4.
, generates the modulated 13.56MHz signal on the
)
IN
OUT
, has to be connected to the external antenna through
REF
)
, provides a reference voltage used by the output
REF
Names, for an overview of the signals
)
Figure 4: CR14 Application
OUT
pin and GND.
2 Signal description
9/46