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REF6025: REF6025 stability

Part Number: REF6025
Other Parts Discussed in Thread: REF5020

Dear Sir, please answer

I asked a question about REF6025 in Jun 2017. Please see my circuit in attach. 

I need to adjust frequency of generator - 16,384,000 Hz. I need to vary voltage in the generator's control input "VC" in the range 1.5 V +/- 30 mV.

We made 5 devices and I measured voltage at the REF6025 outs - they are in the range of 2.501 V to 2.498 V.  I need temperature range from minus 40 to plus 60 C. While we did not check the temperature change. It would be desirable to obtain the maximum possible stability of the voltage in this temperature range.  While at a temperature of 20 degrees, the following is obtained: I adjust the frequency to the nominal with a potentiometer RP1, but then after a while it changes by 15-20 Hz. The reason I can not understand while - maybe the generators are not working very well. Variation of frequency within such limits is a lot  for me. It is probably necessary to review the values of the resistors R7 and RP1?  But the current of this resistor divider should be minimal since my device is powered by a battery. Can you advise something better circuit for voltage adjust?

But that's what I think: since I have enough voltage REF of 2V, can I apply not REF6025 but REF5020?  I think that the smaller the voltage difference from the output of REF from the value of 1.5 V, the less the error?



Vladimir Naumenkov


Picture_Voltage Ref_.docx


  • Hi Vladimir,

    This is interesting. I am unsure of the cause of this voltage difference. Can you measure the voltage on the output of the REF6025 before the frequency shift and after? How big are resistors? Is VC getting sufficient current?

    In regards to the additional questions, the REF5020 will also work but I think it is more important right now to identify the cause of the frequency shift. Also try adding a capacitor on the VC pin to see if that stabilizes the output.

  • Dear Marcoo, thank you


    Vladimir Naumenkov