• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 47 subscribers
  • Views 332 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

ADC78H89: Data converters forum

ttd
Mastermind 9335 points

Part Number: ADC78H89

Dear Technical Support Team,

My system needs to supply AVDD = 5V and DVDD = 3.3V for ADC78H89.

However I forgot to connect DVDD = 3.3V. (Only AVDD =5V ).

It seems that digital interface like DOUT shows approximately 2.3V for high level and it seems operate digital data from AD conversion with its real ability.

Do you know why digital interface like DOUT shows approximately 2.3V without DVDD?

It looks strange behavior.

If possible , could you explain it from equivalent circuit? (For example, ESD diode drop between AVDD and DVDD)

Of course, I have been trying to connect DVDD=3.3V.

Best Regards,

ttd

  • 0
    TI__Guru 51270 points
    Hello,

    We do not have an equivalent circuit that we can share. However, it is not a surprise that there is an internal leakage path that is developing 2.3V on DOUT. This leakage path could be coming from AVDD, or could be coming from one of the other digital inputs with a 3.3V high level on the input, or a combination of both.

    In either case, it is unlikely there will be much drive capability to drive fast edge rates into capacitive loads. You definitely want this power input connected to a voltage source for reliable operation of the device.

    Please also note that AVDD=5V must ramp up before or with the 3.3V DVDD input; at no time can the DVDD pin exceed AVDD by more than 0.3V, or the device could be damaged. Please refer to the 'Power Management' paragraph on page 15 of the datasheet.

    Regards,
    Keith N.
    Precision ADC Applications