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ADR03 Vout adjustment range

Hi All,

One of my customers has one problem with ADR03 output adjustment range.

Part of his circuit schematics is attached.

As shown in the schematic, Vout adjustment circuit is almost the same as shown in the data sheet, Figure 35.

He said that the Vout adjustment range is 2.485 to 2.5005 in his circuit, although data sheet said that adjustment range is 2.3V to 2.8V.

Could you advise us what is the problem in his circuit?

He sent me another question.

The data sheet said that the “ADR01/ADR02/ADR03/ADR06 trim terminal can be used to adjust the output voltage over a nominal voltage”, in page 15. In this sentence, what is the nominal voltage value?

Thank you for your help,

Ricky

  • In addition, nominal voltage refers to the specified output voltage of the ADRXX family i.e. 2.5 V for ADR03.

    I agree with Roel, you might try first to disconnect the REF pin to the ADR03 just to check if you get the circuit on figure 35 correctly. Then we could try to look for a solution just in case that the problem happens when connecting the REF pin to the ADR03.

    Best regards,

    Emman

  • Hi Ricky,

    I tested the circuit in the lab and the Vout adjustment range I measured correlates with the data sheet.

    Can you double check the resistor and capacitor values in the circuit? Also, is it possible to disconnect the output of the ADR03 from the ADC? If it is, could you measure the output of the ADR03 in this condition? It's possible that the REF pin may be loading the output of the ADR03.

    Thanks,

    Roel


  • Hi rvieja-san and Emman.A-san,

    Thank you for your replies.

    I will double check with my customer.

    Thank you again for your help.

    Ricky

  • Hi rvieja-san and Emman.A-san,


    My customer still has the problem.

    He tried according to your suggestions, however still has narrower adjustment range.

    He removed all of road connected to the output terminal of ADR03 and measured adjustment range. The result was around 0.02V range.

    The he made off board test as shown in picture of attached file “ADR03 off board test”.

    When the R1 was 470kohm, the adjustment range was max= 2.5103V, Min=2.4846V, Range=0.0257V.

    He changed R1 value to 2.7kohm (actually two resisters were used 2.05kohm + 2.67kohm).

    The result was max=2.7016V, min=2.2607V, range=0.4409V.

    The adjustment range of 0.02V is too small for his application.

    Question

    1. What is wrong is his test which result is differ from data sheet?
    2. Is it okay to use 4.7kohm for R1 from the point of view of ADR03 internal circuit operation? What resistance value range is allowed for R1?

    Thank you for your help.

    Ricky

  • Hi Ricky,

    I already asked our product experts regarding the possible effects of changing the value of R1 to 4.7 kohms and I will let you know as soon as I heard anything from him.

    Do you know what particular output voltage your customer trying to set? What is the target temperature Coefficient (TC)? It is said that moving the output more than a few millivolts will affect the tempco greatly.  Tempco is one of the most important parameter for a voltage references.

    Best regards,

    Emman

  • Hi rvieja-san and Emman.A-san,


    My customer is awaiting your advice.

    After previous test, he confirmed in his test setup that there are no erroneous phenomenon occurred such as oscillation at all terminals by using oscilloscope.

    Could you advise us what is wrong in his test setup, and what is the cause of this different result from you?

    Also could you advise us what resistance value range is allowed for R1?

    If available, could you let us know the relationship between R1 value and output adjust range?

    Thank you for your help.

      Ricky

  • Hi Emman-san,

    My customer actually needs the adjustment range of 2.485V to 2.51V.

    This is for adjustment of his circuit accuracy variations.

    The TC requirement information was not available from him.

    Thank you for your continued support.

    Ricky

  • This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin