This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADC12D1600: Regarding DNC pin

Part Number: ADC12D1600

Hi

If DNC pin of ADC12D1600 is shorted to power rail or Ground? What will happen? Could you briefly explain?

Regards,

Aravindhan R

  • Aravindhan,

    We are looking into this.

    Regards,

    Jim

  • Aravindhan,

    The pins that may cause a problem if connected to power or GND is D7 and U7. The others probably will  not cause a problem.

    Regards,

    Jim

  • Hi Aravindhan,

    Depending on which pins are connected to Ground or power can have different effects.

    Can you please share what pins are connected and to what voltage level?

    Regards,

    Rob

  • Hi Rob

    I want to know the effects when all DNC(D1,D7,E3,F4,W3,U7) pins get shorts to power or GND. The voltage level will be 1.9V.

    Regards,

    Aravindhan R

  • Hi Jim

    Could explain briefly why that particular pin have some problem and also why others doesn't cause? and also tell what functionality will get affected if that short to GND or Power.

    regards,

    Aravindhan R

  • Hi Aravindhan,

    D1, is probably okay, it has an internal pull-down or pull-up inside the IC.

    D7 and U7 are connected to circuits inside the IC. These are the most critical and should not be connected to PWR or GND.

    E3 and F4 are connected to circuits inside the IC. These are high-impedance. Not sure of the cause when connected directly to PWR or GND.

    W3 is connected to circuits inside the IC. Not sure of the cause when connected directly to PWR or GND.

    We feel it would be best to modify the PCB layout to remove these connections to PWR and GND altogether.

    Regards,

    Rob

  • Hi Rob

    I need this information for doing FMEA in that I need to describe exact failures of IC. From your response,I can get idea that D7 and U7 are connected to internal circuits and those have severe effects when shorts to Pwr or GND. But I want to know the internal circuits for each DNC pin and also exact functional failures of IC when each DNC shorts to Pwr or GND. Your explanation will help me to know the exact functional failure. Kindly response

    Thanks and regards,

    Aravindhan R

  • Hi Aravindhan,

    Unfortunately, we just don't have that kind of information on forcibly trying to break a device in the lab and understanding the failures associated with connecting the recommended DNC pins to ground or power.

    It is advised that the board design be updated per the datasheet DNC pins outlined in the datasheet.

    Regards,

    Rob

  • Hi Aravindhan,

    I have some additional information that came back from the design team today regarding pins D7 and U7.

    "Shorting high for even short periods may cause device failure. There is an ESD diode from these pins. If 2V forward bias on this ESD diode with no current compliance may cause the ESD diode to fail, permanently shorting the on-die generated negative charge-pump voltages to ground."

    Hopefully you find this helpful.

    Regards,

    Rob

  • Hi Rob

    Yes this information is helpful. Could you get back further information from design team about the internal circuits for all DNC pins and exact failure modes?.

    Because I need these details to write failure cases in Failure mode analysis.

    Thanks and regards,

    Aravindhan 

  • Hi Rob 

     My query is not yet resolved. 

    Could you get back further information from design team about the internal circuits for all DNC pins and exact failure modes?.

    Because I need these details to write failure cases in Failure mode analysis. Could you reply as soon as possible.

    Thanks and regards,

    Aravindhan 

  • Hi Aravindhan,

    I understand your concern but we have not characterized the exact failure modes that will occur when a power or ground event will happen on these various DNC pins.

    The information below, is all I have from the design team.

    Regards,

    Rob

    ·  Pin D1 is a CMOS input pin with 500 ohm series and 50K pull up. Shorting this pin high or low changes operation but no reliability impact.

    ·  Pins D7 and U7 are connected to the on-die generated negative charge-pump voltages. Shorting either pin low causes device’s I or Q channel to stop converting correctly for the duration of the short. Shorting this pin high for even short periods may cause device failure. There is an ESD diode from these pins (anode) to GND (cathode), and a 2V forward bias on this ESD diode with no current compliance may cause the ESD diode to fail, permanently shorting the on-die generated negative charge-pump voltages to ground.

    ·   Pins E3 and F4 are for design diagnostics.  Shorting high/low while using PIN control mode or datasheet document SPI settings does not change operation and has no reliability impact.

    ·   Pin W3 is a digital output for SCAN and design diagnostics.  Shorting this pin to a high low voltage may cause failure of the output driver, but this is not required for the ADC to operate. Worst case, this will cause residual leakage currents.