MUX
RX_IN1
RX_IN2
Phase and
Amplitude
Detector
Gain
RSSI
(AUX)
Logic
Level
Shifter
State
Control
Logic
(Control
Registers and
Command
Logic)
127-Byte
FIFO
MCU
Interface
VDD_I/O
I/O_0
I/O_1
I/O_2
I/O_3
I/O_4
I/O_5
I/O_6
I/O_7
IRQ
SYS_CLK
DATA_CLK
ISO
Protocol
Handling
Decoder
RSSI
(External)
Gain
RSSI
(Main)
Filter
and AGC
Digitizer
Bit
Framing
Framing
Serial
Conversion
CRC and Parity
Transmitter
Analog Front End
TX_OUT
VDD_PA
VSS_PA
Digital Control
State Machine
Crystal or Oscillator
Timing System
EN
EN2
ASK/OOK
MOD
OSC_IN
OSC_OUT
Voltage Supply Regulator Systems
(Supply Regulators and Reference Voltages)
VSS_A
VSS_RF
VDD_RF
VDD_X
VSS_D
VSS
VIN
VDD_A
BAND_GAP
RF Level
Detector
Phase and
Amplitude
Detector
Copyright © 2017, Texas Instruments Incorporated
16
SLOS743L – AUGUST 2011 – REVISED MARCH 2017
Product Folder Links:
Detailed Description
Copyright © 2011–2017, Texas Instruments Incorporated
6.1.3.3
Card Emulation
The chip can enter this mode by setting appropriate option bits. The chip can emulate ISO/IEC 14443 A
and B card types. For ISO/IEC 14443 A and B, the emulation supports 106-kbps data rate to start. For
ISO/IEC 14443 A, the anticollision algorithm can be performed using an internal state machine, which
relieves the MCU of any real-time tasks; however, this method can present interoperability challenges with
other NFC devices due to timing requirements. To ensure best interoperability, TI recommends allowing
the MCU to manage the anticollision process, instead. The unique ID required for anticollision is provided
by the MCU after wakeup of the system.
6.2
System Block Diagram
shows a block diagram of the TRF7970A.
Figure 6-2. System Block Diagram
6.3
Power Supplies
The TRF7970A positive supply input V
IN
(pin 2) sources three internal regulators with output voltages
V
DD_RF
, V
DD_A
and V
DD_X
. All regulators use external bypass capacitors for supply noise filtering and must
be connected as indicated in reference schematics. These regulators provide a high power supply reject
ratio (PSRR) as required for RFID reader systems. All regulators are supplied by V
IN
(pin 2).
The regulators are not independent and have common control bits in register 0x0B for output voltage
setting. The regulators can be configured to operate in either automatic or manual mode (register 0x0B,
bit 7). The automatic regulator setting mode ensures an optimal compromise between PSRR and the
highest possible supply voltage for RF output (to ensure maximum RF power output). The manual mode
allows the user to manually configure the regulator settings. For applications in which the TRF7970A may
be subjected to external noise, manually reducing the regulator settings can improve RF performance.