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Original question:

TRF7963A: TRF7963

TRF7963A: How can realize TRF7963 switch between standby mode and full /half output power mode by the way of the ID card near or away Reader？

Yulei Wang
Prodigy 145 points
Part Number: TRF7963A

Hi TI engineer

          We use TRF7963 on RFID reader to read Personal ID Card complied with ISO14443B standard.

We found the system power consumption was very high when TRF7963 was working on full or half output power mode all the time.we want to realize TRF7963 can goin to standby mode when none RFID card close to RFID reader？For example,the communication stop(go to end) between ID Card and Reader, whether a signal of TRF7963 can indicate the communication state change？the signal can notice MCU control TRF7963 goin to  standby mode.The next step，whether a signal of TRF7963 can indicate the ID card close to the antenna of Reader？the signal can notice MCU control TRF7963 go back to full/half output power mode.

If we can control TRF7963 switch between standby mode and full /half output power mode by the way of the ID card near or away Reader,we can reduce the system power consumption obviously.

What do you suggest for our application?

Thanks

  • 0
    TI__Guru*** 135355 points

    Hello Yulei,

    Yulei Wang said:
    For example,the communication stop(go to end) between ID Card and Reader, whether a signal of TRF7963 can indicate the communication state change？

    This would be a software determination by the MCU controlling the device. The TRF7963A is just an NFC transceiver and it's 'smarts' are limited to telling the MCU when data is available, and having registers that can be read to inform on status.

    What can be done on software is that if a transaction is finished, the RF field can be turned off for a period of time before being restarted again.

    Yulei Wang said:
    The next step，whether a signal of TRF7963 can indicate the ID card close to the antenna of Reader？

    There are two methods to handle this. One is simple but less power saving, however it may be sufficient for your use case. The other is advanced, requires hardware modifications, but offers the best power savings.

    1) Simple software handling

    Rather than keep the field on at all times, poll for tags with a set sequence and then keep the RF field off. In our NFC stack, we keep the NFC field off for about 80% of the time when polling for all modes. If you are limited to just ISO14443B, you can save even more time and keep the field off close to 95% of the time. The idea is to turn the field on every 500ms, leave it on for the guard time required to charge an ISO14443B card within the proximity, and then issue polling command. If a tag is present, it will be reply, and then enter to full communication sequence. If a tag is not present, then turn off the RF field and wait 500ms to try again.

    We found 500ms is a good sweet spot for power savings and user experience, but you can increase/decrease that interval as you see fit.

    For better power savings, this would need to go hand in hand with my reply from question 1 which is that software should determine when reading is concluded and then turn the field off. This way you don't have someone hold the tag in place for 5-10 seconds and blast the RF field the entire time. You could even set it where if when reading is concluded, there is a timeout of 5 or 10 seconds before another tag can be read - if it makes sense in your system.

    2) Advanced method w/ Hardware modifications

    The TRF7963A is not, on it's own, capable of detecting the presence of a tag without turning on the RF field and issuing a command. However, one of our former apps experts devised a clever method to identify a tag is approaching and alert the MCU. This process has been fully documented in the following app note: http://www.ti.com/lit/pdf/sloa184

    I would recommend trying method #1 first and see if the power savings are sufficient, as method #2 is more likely to require higher effort to implement fully.