Overview; Power Supplies - Texas Instruments TRF7960 Manual

TRF7960, TRF7961
SLOU186G – AUGUST 2006 – REVISED MAY 2017
6 Detailed Description
6.1

Overview

Figure 6-1 shows a typical application diagram for the TRF796x devices. A parallel or serial interface can
be implemented for communication between the MCU and reader. Transmit and receive functions use
internal encoders and decoders with a 12-byte FIFO register. For direct transmit or receive functions, the
encoders and decoders can be bypassed so the MCU can process the data in real time. The transmitter
has selectable output power levels of 100 mW (20 dBm) or 200 mW (23 dBm) into a 50-Ω load (5-V
supply) and supports ASK or OOK modulation. Integrated voltage regulators ensure power-supply noise
rejection for the complete reader system.
Impedance
Matching
Circuit
Data transmission supports low-level encoding for ISO/IEC 15693, modified Miller for ISO/IEC 14443 A,
high-bit-rate systems for ISO/IEC 14443, and Tag-it coding systems. Included with the data encoding is
automatic generation of SOF, EOF, CRC, and parity bits.
The receiver system enables AM and PM demodulation using a dual-input architecture. The receiver also
includes an automatic gain control option and selectable gain. Also included is a selectable bandwidth to
cover a broad range of input subcarrier signal options. The received signal strength for AM and PM
modulation is accessible through the RSSI register. The receiver output is a digitized subcarrier signal
among a selectable protocol and bit rate as outlined in
and a data clock as outputs.
The receiver system also includes a framing system. This system performs a CRC or parity check,
removes the EOF and SOF settings, and organizes the data in bytes. Framed data is then accessible to
the MCU through a 12-byte FIFO register and MCU interface. The framing supports ISO/IEC 14443 and
ISO/IEC 15693 protocols.
The TRF796x supports data communication levels from 1.8 V to 5.5 V for the MCU I/O interface, while
also providing a data synchronization clock. An auxiliary 20-mA regulator (pin 32) is available for
additional system circuits.
6.2

Power Supplies

The positive supply pin, VIN (pin 2), has an input voltage range of 2.7 V to 5.5 V. The positive supply input
sources three internal regulators with output voltages V
capacitors for supply noise filtering. These regulators provide enhanced PSRR for the RFID reader
system. Table 6-1
10 Detailed Description
VDD_X
TX_OUT
TRF796x
RX_IN1
RX_IN2
OSC_IN OSC_OUT
Crystal
13.56 MHz
Figure 6-1. Typical Application Diagram
describes the power supplies.
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SYS_CLK
DATA_CLK
IRQ
3 (SPI) or 8 (Parallel)
VDD_I/O
Copyright © 2017, Texas Instruments Incorporated
Table 6-13. A selected decoder delivers bit stream
, V , and V
DD_RF DD_A
Copyright © 2006–2017, Texas Instruments Incorporated
TRF7960 TRF7961
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VCC
MSP430 MCU
that use external bypass
DD_X