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TMS570 usb - adc issue

Eric Newnam
Prodigy 90 points

Other Parts Discussed in Thread: TMS570LS20216

I am trying to figure out the ADC on the TMS570LS20216 Usb demo board. I searched for a while and could not find out what the voltage range of the ADC with this set up. So i decided to measure it. I used pin 0 on ADC 1. I hooked an adjustable power supply across a ground pin and pin 0. I slowly increased the voltage taking periodic measurements. As i approached 3.3v the power supply jumped to 4v.  now the out put of the ADC conversion reads about 3795 no matter what voltage is applied.

Did I fry the ADC, just that pin, all pins on ADC 1, both ADC 1 and 2.

  • 0
    TI__Mastermind 22715 points

    Eric,

    I am afraid that the ADC input pin is shorted to 3.3V internally. You should never directly hook up a power supply to any I/O pin. It is be done via a 5-10k resistor. There are clamp diodes inside the device to limit the voltage visible to the input buffer. You can try using other ADC pins to see it would work.

    Thanks and regards,

    Zhaohong