REF OUT of AD7245AAR and AD7245AARZ

Dear Madam/Sir;

Hi;

I am Matiu from P-techno group company in Shenzhen

I have a question about IC AD7245AAR and AD7245AARZ.

What is the range of REFERENCE VOLTAGE (pin no.3) in these both ICs?

Based on Data sheet, it should be 4.99 V to 5.01 V at 25C.

But one of our customer can accept only between 5.000 V to 5.009 V when VDD=15 V

In data sheet of this IC, one diagram is reference voltage VS temperature  as shown below:

By considering this diagram, does it mean that reference voltage (Pin No.3 in IC) should be between 5.000 to 5.009?

Please guide me and let me know your comment.

Best regards.

  • 0
    •  Analog Employees 
    on Feb 9, 2021 6:14 AM

    Hi Matiu,

    The TPC4. plot is only a Typical plot, means that this plot only shows the most common response that you can read out of the part.

    There are couple of things that affects the output of the REF OUT pin:

    1. Initial Accuracy - in this case it is the "REF OUT @ 25degC". This means that when measuring the output of the REF OUT pin, you will see a voltage between 4.99V to 5.01V.
    2. ∆REF OUT/∆VDD - every change in supply of the part, there is a corresponding change in output of REF OUT Pin.
    3. Temperature Coefficient - this is the TPC4 plot above.
    4. Load Change - every change in load current of the part, there is a corresponding change in the output of REF OUT Pin.

    These things can add to each other. 

    Regards,

    Mon

  • I have another question, what is different between initial accuracy and relative accuracy? and which of them affects on output? for example our IC is AD7245AAR and relative accuracy is +_3/4 LSB, if we consider it it means that out put  range accuracy should be +-0.00366?Please let me know you comment

  • 0
    •  Analog Employees 
    on Feb 23, 2021 2:55 AM in reply to mdashti

    Hi Matiu.

    The initial accuracy I'm talking about is that for 2.5V voltage reference it will deviate per part. For example you have 3 AD7245, unit 1 can be 5.01V and unit 2 can be 5 and unit 3 can be 5.99. Though it will stay the same per unit even if you power cycle it.

    For the relative accuracy, it is a measure of the actual deviation from a straight line passing through the endpoints of the DAC transfer function. It is measured after allowing for zero and full scale and is normally expressed in LSBs or as a percentage of full-scale reading.

    Regards,

    Mon