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RF430CL331H: Minimum supply voltage for RF430CL33x

Stanislaw Skowronek1
Prodigy 80 points
Part Number: RF430CL331H

The RF430CL331H datasheet has two specified operating ranges for VCC: "during program execution no RF field present" at 3.0 - 3.6V and "during program execution with RF field present" at 2.0 - 3.6V. Can you explain when the 3.0V Vcc minimum is relevant? The sensor tag kit documentation says it requires 2.2 - 3.6V in section 1, "Key System Specifications" and I have verified that it does indeed function at those voltages.

  • 0
    TI__Guru*** 128355 points
    Hello Stanislaw,

    If the device is powered by RF field, then 2V is okay, but if the device is only powered by VCC with no RF field from an NFC/RFID reader present, it requires 3V.

    Can you link the document for the 'sensor tag kit'? Not sure which one you mean.
  • 0 in reply to Ralph Jacobi
    Prodigy 80 points

    Right, that's basically what it says. But what does "during program execution" mean (yeah, I understand it's a 430 inside - but I am not aware of its programming, or when it sleeps; I saw one of the earlier answers mentioning VCORE pin changes to ~1.5V - does this correspond to program execution)? Does it mean that the LOOPING_READ errata patch may fail if initiated without external field and at <3.0V?

    The exact TI document I was thinking of is TIDU821, page 2. See: www.ti.com/lit/ug/tidu821/tidu821.pdf

    Thank you for your time,

    Stan

  • 0 in reply to Stanislaw Skowronek1
    TI__Guru*** 128355 points
    Hello Stan,

    Program execution means anytime the device is outside of LPM modes and doing active processing. In a properly designed system, this should only occur under 2 situations.

    1) RF reader presents itself and an RF field is present as the tag executes code and handles NFC communication
    2) The host MCU talks to the tag without an RF reader present to read/write data or configure registers such as enabling RF.

    The CL331H requires a decent amount of communication with the MCU during NFC transactions but otherwise it can sit untouched after initial setup.

    If you mean would the LOOPING_READ errata patch fail if the write sequence to the device was done without an RF field present, then yes.

    One method to avoid that is that as soon as the RF field is detected, write the registers for errata patch and then enable RF. The NFC guard time, if the MCU executes fast enough, should allow for that to all be done before sending the first poll command.
  • 0 in reply to Ralph Jacobi
    Prodigy 80 points
    Great! Thank you very much for the detailed & helpful answer.