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CRX14_10 Datasheet, PDF (10/47 Pages) STMicroelectronics – ISO14443 type-B contactless coupler chip with anti-collision, CRC management and anti-clone function
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Signal description
CRX14
2.6
Serial data (SDA)
The SDA signal is bi-directional. 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 connected from Serial data (SDA) to VCC. (Figure 5
indicates how the value of the pull-up resistor can be calculated).
2.7
Chip enable (E0, E1, E2)
The Chip Enable inputs 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 VCC or GND to establish the Device
Select Code (note that the VIL and VIH 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 resistors connected to each inputs.
2.8
Power supply (VCC, GND, GND_RF)
Power is supplied to the CRX14 using the VCC, GND and GND_RF pins.
VCC is the Power Supply pin that supplies the power (+5V) for all CRX14 operations.
The GND and GND_RF pins are ground connections. They must be connected together.
Decoupling capacitors should be connected between the VCC Supply Voltage pin, the GND
Ground pin and the GND_REF Ground pin to filter the power line, as shown in Figure 4.
Figure 4. CRX14 application schematic
VCC
OPT
R1
E0
0R
R2
C6VCC
100nF50V
OPT
OPT C3 WURTH 742-792-042U1
R3
FL7
R5
22nF50V
E1
0R E2
0R
R4
R6
1
2
3
4
5
6
7
8
VREF
VCC
RFIN RFOUT
E0 GND_RF
E1
OSC1
E2
OSC2
GND_RF GND
GND
SCL
GND SDA
16
15
14
13
12
11
10
9
CRX14
C8
100pF50V
C8'
C1 7pF50V 8pF50V
D1
1N4148 (OPTIONAL)
C5
10pF50V R8
0R
ANT1
X1
13.56MHz
C2 7pF50V
C7
C7'
120pF50V 33pF50V
J1
SDASCL
FL5 0R
4
3
2
FL4 0R
1
FL6 0R
VCC
+ C4
22uF 10V
R7
ANT2
0R
AI10952
10/47
Doc ID 8880 Rev 4
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