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SLOS743L – AUGUST 2011 – REVISED MARCH 2017
Product Folder Links:
Applications, Implementation, and Layout
Copyright © 2011–2017, Texas Instruments Incorporated
7
Applications, Implementation, and Layout
NOTE
Information in the following Applications section is not part of the TI component specification,
and TI does not warrant its accuracy or completeness. TI's customers are responsible for
determining suitability of components for their purposes. Customers should validate and test
their design implementation to confirm system functionality.
7.1
TRF7970A Reader System Using SPI With SS Mode
7.1.1
General Application Considerations
shows and application schematic optimized for all TRF7970A modes using the Serial Port
Interface (SPI). Short SPI lines, proper isolation of radio frequency lines, and a proper ground area are
essential to avoid interference. The recommended clock frequency on the DATA_CLK line is 2 MHz. This
figure also shows matching to a 50-
Ω
port, which allows connecting to a properly matched 50-
Ω
antenna
circuit or RF measurement equipment (for example, a spectrum analyzer or power meter).
7.1.2
Schematic
shows a sample application schematic for SPI with an SS mode MCU interface.
Figure 7-1. Application Schematic – SPI With SS Mode MCU Interface
Minimum MCU requirements depend on application requirements and coding style. If only one ISO
protocol or a limited command set of a protocol needs to be supported, MCU Flash and RAM
requirements can be significantly reduced. Recursive inventory and anticollision commands require more
RAM than single slotted operations. For example, an ISO/IEC 15693-only application that supports
anticollision needs approximately 7KB of flash memory and 500 bytes of RAM. In contrast, a full NFC
stack that supports peer-to-peer, card emulation, and reader/writer modes needs 65KB of flash memory
and 4KB of RAM. An MCU that can run its GPIOs at 13.56 MHz is required for direct mode 0 operations.