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ADC128D818: Detailed informations about internal reference block of ADC128D818 are needed.

Sunghyuk Choi94
Prodigy 20 points
Part Number: ADC128D818

Hi, I'm Choi.

I would like to find out detailed information about ADC128D818's internal reference circuit.

Because I use ADC128D818 with its internal reference voltage function, I want to know the reliability

of the internal reference block. 

What kind of method does the ADC128D818 use for internal voltage reference?

I can't find out detailed information about the block?

What does the block(Internal reference block of the ADC128D818) include in it ? 

Does the block have diode ?

Is there a independent IC that have same circuits with ADC128D181's internal reference block?

I have a PBA with ADC128D818, and I don't want to change the schematic for the PBA to use external voltage reference IC.

But I worry about the reliability of internal reference block of the ADC128D818.

Could you give me some application note or white papers or datasheet about ADC128D818 ?

Thanks all to read this requests.

  • 0
    TI__Guru**** 180771 points
    Hi Choi,

    Welcome to our e2e forum!

    I don't have any application notes or white papers regarding the reference of the ADC128D818 specifically. What are your main concerns about the internal reference? Drift over temperature? Initial accuracy? You mention reliability, but I am not sure exactly what you mean by that, if you can explain with a little more detail, that would be great.
  • 0 in reply to Tom Hendrick
    Prodigy 20 points
    Hi Tom,

    I'm glad to receive first reply from you as fast as this.

    I mainly concerns about drift over temperature and drift over input supply voltage.
    I read 23ppm/ºC for internal reference voltage as typical value from datasheet, but there is no min, max values for it.
    And, according to the datasheet, the typical value of internal reference voltage is 2.56V. but, min, max value is not informed.
    Could you let me know what kind of components or methods are used for internal reference block ?
    Does the block use diode ?
    To figure out the operation of the internal reference block, I want to know some more detailed structure of the block.
    Our temperature condition for operation ranges from -40 to 85 celsius degree.
    I mentioned 'Reliability' at my first post. I would like to change it to 'Stability'.
    How does the internal reference keep stable value,2.56V, over temperature or input voltage ?

    If the temperature is -40 celsius degree, is the internal reference voltage is just near 2.558375~ 2.57625?
    [ 23ppm/ºC applied for drift. (25- (-40))*23*10^6= 0.001625]
  • 0 in reply to Sunghyuk Choi94
    TI__Guru**** 180771 points
    Hi Choi,

    I will look to see what sort of detail I can provide. It might take a day or two to dig out the design archive, so I will try to get back to you tomorrow on this.
  • 0 in reply to Tom Hendrick
    TI__Guru**** 180771 points
    Hi Choi,

    Some detail I found in the characterization data implies that the internal reference is trimmed to the 2.56V typical spec. It is not production tested, which is why there is no min or max specification. For informational purposes only, the distribution had a guard band of +/- 300uV.