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TMS320F280049C: MCU Power on Question

Johnny Chen
Expert 5130 points
Part Number: TMS320F280049C


Hi Champ,

I am asking for the customer. They are concerning the situation as below.

Before MCU power on, ADC or GPIO pin is replied a 3.0 volt. After a few seconds, VDDIO start to raise from 0V to 3.3V.

The datasheet specifies that  this may permanently damage the device because the current(>20mA) will be reversely go into VDDIO through ESD diodes.

At the condition of reverse current is smaller than 20 mA, first question is : Does DSP work normally or it would latch up ?

Follow up question, if DSP could work normally, how could DSP make it ? The mechanism of POR or others ?

If the DSP fails to work normally, is there any method suggested to solve or prevent it ?

I am grateful for any help. Thanks !

BR, Johnny

  • +1
    TI__Mastermind 39620 points

    Hi Johnny,

    It is not recommended to have any input pins on the F280049 be biased or at some voltage level prior to the DSP power up.  This will cause a lot of issues.  Latch up may be one when the clamp current will be high and might damage the part.  Having a voltage in the inputs would potentially introduce some power into VDDIO through the ESD diodes and this might be enough to cause some degradation in the internal oscillator (see errata SPRZ439F on INTOSC advisory) for instance if this condition is repeated over time.

    One workaround is to add an external reverse biased diode with a series resistor on the affected input pin, such that if VDDIO is not powered yet, the input signal would propagate to the external diode/resistor instead.

    Regards,

    Joseph