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F2802x - Power Sequencing

sugita
Intellectual 270 points


Hello All,

 

I have a question about power sequencing of F2802x. SPRS523F (page 8) says that we don't need Power Sequencing, if we don't care glitch on I/O pins. I can understand it.

 

My question is Page 91(6.9 Power Sequencing). This section says "don't apply power to any pins before powering the device". 

What is "unpredictable results" ? Does glitch on I/O pins make trouble for other parts on the board?  Or F28027 doesn't work properly?

 

Thanks

 

Morgan

  • 0
    TI__Expert 8500 points

    Nathan,

    The statement saying there is no power sequencing requirement means that there is no requirement on the order of the power rails. True you could argue that the section saying not to apply voltage to any pin prior to powering the device is sort of a power sequencing requirement in itself. Sorry for the semantics, we have tried to put all the pertinent information into the datasheet. As to your question the term "unpredictable results" comes from some historical data that showed when too great of a voltage was applied to the ADCIN pins prior to powering the device odd behavior in other areas of the device (PWM pins, oscillator, etc.) occurred. The exact behavior was unpredictable, however, in each case the issue reamined until power was cycled without the voltage on the ADCIN pin. I'm not sure if this behavior has ever been seen on digital I/O pins, but after analyzing it we could not rule it out.

    Regards,
    Dave Foley

     

  • 0 in reply to David Foley
    Intellectual 270 points

    Dave,

    Thank you for detailed explanation. I clearly understood.

    Regards,
    Morgan