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# Formula for ADR0x TRIM resistors

I would like to use the TRIM pin with fixed resistors rather than a potentiometer to set the ADR01 output to a voltage other than nominal, within the specified adjustment range.  Is there a formula to determine the appropriate resistor values?  I could breadboard it then measure the potentiometer setting, but if you can provide a formula, that would be quicker and easier.

• Hi,

Thank you for your question. I'll ask the product expert on this device to verify if we can provide the equation for the trim pin and get back to you soon.

Regards,

Phil

• If a formula cannot be provided then I would appreciate simply knowing the resistor values for R2 and R3 that would provide an output voltage of 10.03V.  Thanks.

• Hi,

Please see image below for your reference. This is a representation of the device with internal resisitor value. Please take note that this is not the actual device but just a behavioral model so that we can estimate the resistor value.

Now, we might choose the value of R5 and R6 correctly but given the fact that these resistors has tolerances, it is highly possible that we cannot get the exact value and will show different voltage in reality. Also, the part itself  has +/10 mV of error from the initial voltage so we should expect that additional error will be added  to the resistor divider. That is why it is highly recommended to use  potentiometer to adjust the output voltage to the desired output.

I have a question, why do you need 10. 03 V reference or on what application are you using this part?

Regards,

Phil

• I am using the ADR01 to generate a 10V reference input to a DAC.  I am using an AMP03 to produce the -10V reference.  I was getting some glitch noise on the DAC output, so, I added a lowpass filter to the negative reference input.  The reference input has an input resistance, so my filter was causing a slight attenuation in the reference voltage.  The 10.03V figure is to compensate for this loss.