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ADS8528: ADS8528 HVDD, HVSS voltage range

Saemyi Jeon
Intellectual 1110 points
Part Number: ADS8528

 

Hi All,

 

I am writing this to ask about the HVDD/HVSS voltage range of ADS8528.

 

We are trying to replace MAX1312 with ADS8528 in customer system.

They can use only +/-12V voltage for HVDD and HVSS in their system but the range of input voltage is +/-10V. So, customer has some question on the voltage range of analog input. Would you please answer below questions? 

  •  When the analog input voltage with +/-10V is used, could +/-12V be used for HVDD and HVSS? Or they can use the HVDD and HVSS less than 12V?
  • How much margin can the analog input have based on the HVDD and HVSS?
  • Looking at the datasheet, it seems that the analog input voltage is related to VREF. Should they consider only VREF for the analog input voltage range?

 

Thanks.

Best regards,

Sammy

  • 0
    TI__Intellectual 1110 points

    Hi All,

    Can I get your answer?

    Best regards,

    Sammy

  • 0 in reply to Saemyi Jeon
    TI__Guru**** 168485 points

    Hi Sammy,

    There is no issue using the ADS8528 with +/-10V in and +/-12V HVSS/HVDD.  The analog input range is either +/-2Vref or +/-4Vref - since the internal Vref is 2.5V, they can use the +/-4Vref option and use the full +/-10V input range of the ADS8528.

  • 0 in reply to Tom Hendrick
    TI__Intellectual 1110 points

    Hi Tom,

    Thanks for your answer.

    I have one more question about the relationship between HVDD/HVSS and the analog input.

    As I mentioned, I am trying to replace MAX1312 with ADS8528. MAX1312 doesn't require HVDD/HVSS even though input voltage range is +/-10V.

    Since there is no high voltage rail like 12V and 15V in the current system,  they might need to add a device to make HVDD/HVSS. 

    So, customer doesn't want to add new device for HVDD/HVSS but would like to reduce this voltage to the supply voltage of the used opamp which is 11.5V.

    For that reason, my customer would like to know how much margin of HVDD/HVSS is required based on the analog input voltage to utilize the existing power rails.

    • Could you let me know how much margin of HVDD/HVSS is required based on the analog input voltage?
    • Is +/-10V HVDD/HVSS acceptable to use +/10V Vin? 
    • Or, HVDD/HVSS should be higher as specific voltage than the analog input voltage? If yes, what is the minimum voltage gap between HVDD/HVSS and the analog input voltage to be allowable.

    Best regards,

    Sammy

  • 0 in reply to Saemyi Jeon
    TI__Guru**** 168485 points

    Hi Sammy,

    I can't think of any reason why you could not use the 11.5V rails that you currently have for the amplifiers.  There is no internal buffer for the ADS8528, so there should not be any head room requirements.