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ADC16DX370 SDO protection

Berlauber
Intellectual 260 points

Hello,

As SDO output is 3V by default, I would like to add circuit protection in order to clamp the output to 1.8V to avoid damage in case of error programming.

The datahseet says " A low-capacitance protection diode may also be added with the anode connected to the SDO output and the cathode connected to the desired voltage supply to prevent an accidental pre-configured read command from causing damage" 

Is also suitable for the chip to put a zener (with Vzener=1.8V) between SDO and ground?

Thank you so much

Best regards

  • 0
    TI__Expert 4340 points

    Yes, a zener would work as well. Keep an eye on the capacitance to GND to ensure that it does not prohibit logic transitions at the desired clock rate.

    Regards, Josh

  • 0 in reply to Joshua Carnes
    Intellectual 260 points
    I found that zeners with low Vz (1.5 , 1.8V)have a capacitance of about 180pF, is it acceptable? Does TI recommend any diode part number? zener or not... I want to clamp to 1.8V or less.
    Thank you for all your help with this chip Josh

    Best regards
  • 0 in reply to Berlauber
    TI__Expert 4340 points
    assuming something like 10ohms for the output impedance of the SDO output, the RC time constant with a 180pF would be 1.8ns. This may be a little too long (with output impedance uncertainty) for data transfer at the full 20Mb/s, but it should run just fine at something like 1Mb/s. Also , you want a zener that turns on slightly above 1.8V because you don't want it to turn on every time the logic value goes high.
    Regards, Josh