Alternatively, the power harvested by the NTAG I2C tag chip can also be applied directly as a source of power for devices requiring less energy, such as low power microcontrollers, sensors, and indicators.
The NTAG I2C tag chip’s energy harvesting capability and Field Detect (FD) functions work together to help support power management. Upon application of the RF field to the antenna, the FD output asserts low, and the energy harvested by the NTAG I2C tag chip from the RF field is output (VOUT) to a Power Management Unit (PMU) (1). The PMU distributes received power to both the NTAG I2C tag chip and the microcontroller (2), which allows the I2C bus to become active (3), enabling communication.
For data transfer after communication has been initiated, the on-chip, 64-byte SRAM preserves EEPROM access limits by supporting a data pass-through option. In this case, data flows from the NFC interface through an SRAM buffer to the I2C serial bus interface or vice versa. The NTAG I2C tag chip operates as a modem when in this mode.
When manufacturers embed the NTAG I2C tag chip into products, users can download information via the RF interface to those products even when they are not receiving power, because the NTAG I2C tag chip acts as a connection between the user’s NFC-enabled mobile device and the sealed and packaged product.
With a power to the device off, the contactless NFC interface can still operate, receiving data that the NTAG I2C tag chip stores in nonvolatile EEPROM memory. Later, when the device has power, the microprocessor can access the previously written data via the I2C serial bus interface. Similarly, the microprocessor can write data to the EEPROM while powered for later access via the NFC interface whether or not the device has power.