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BUF16821-Q1: output voltage calculation

Patrick Chen(TPE System & Application)
Expert 3430 points
Part Number: BUF16821-Q1

Hi Sir,

My customer is using BUF16821-Q1 on their system and set the V16 as 35(Dec) with VS =13.5V.

My question as below.

1. Based on Equation1 on the page 10 of spec, The expected voltage on V16 should be Vout=13.5V*35/1024 = 0.4614V, is that correct?

2. On the page3 of the spec, the output accuracy should be +/-50mV, which mean that the output voltage on V16 should be 0.4114V~0.5114V, is that correct?

3. Customer measure the board(10 unit), the measured voltage is around 0.396V which is much lower than we expect, is that normal? What we could check to see if there is any abnormal on the setting?

Many thanks,

PAtrick 

  • 0
    TI__Mastermind 18550 points

    Hello Patrick,

    Thank you for your post. I have assigned this thread to the engineer responsible for supporting this device but due to US holidays, response may be delayed.

    Kind Regards,

    Liaqat

  • 0
    TI__Mastermind 18550 points

    Hello Patrick,

    Since you made this thread urgent, I went ahead and reviewed the datasheet myself instead of waiting for the expert on this device to come back from holidays. Based on my review of the datasheet, here are answers to your questions.

    1. Yes, it is correct.

    2. For this, we need to consider measurement condition. As you can see from curves in figures 2 and 3 in the datasheet, nominal voltage output of the DACs will be dependent on the load. So we can not consider this 50mv accuracy as absolute value over the entire load current range. Rather this 50mv should be considered as accuracy from the nominal value at a given load current.

    3.  I suspect that customer is seeing lower DAC output due to increased load. Again, please use curves in figures 2 and 3 to account for lower voltage due to load current.

    I hope this explanation is helpful.

    Kind Regards,

    Liaqat