Amplitude Resistor for AD698 and CNO301

Hi MJMielke ,

Can you provide more details on your setup? 

• On what pins are you measuring the excitation voltage from? 
• Are you using the evaluation software specific for the CN0301 board?
• What revision of the CN0301 board do you have?
• Just for confirmation, can you try to measure the voltage across J1:1 to J1:5 using a multimeter that is set to read AC voltages?

If possible, do you have any photos of your current hardware setup?

This existing thread might also have some useful information: (+) CN0301 output voltage change - Q&A - Reference Designs - EngineerZone.

Thank you in advance the information you will provide.

Regards,
Andy

Hello,

The CN0301 evaluation board has not come in yet, but I am trying to understand how the 6.98k resistor sets a 3.5 Vrms excitation signal when from the datasheet it looks like it should set a value closer to 5 Vrms excitation. I am reviewing the schematics for Rev A of the CN0301. Is there a new revision?

Regards,
Michael

Hi MJMielke ,

As per the CN0301 Circuit Note (page 3), the expected output excitation voltage is from 0 V to 5V with the 6.98kohm resistor installed between LEV1 and LEV2 pins. 

Upon checking the available design files from the CN0301 product page are Rev A. There is a Rev C version of this board, and the test documentation confirms the output within the expected limits of 0 to 5V. I will just confirm where we can get the design files and try to provide them here.

Regards,
Andy

Hi MJMielke ,

Attached is the CN0301 Rev C schematic. The design files available from the CN0301 product page will be updated soon.

CN0301_RevC_Schematic.zip

Regards,
Andy

Hello,

I believe the 0 V to 5 V output does not refer to the EXC1 and EXC2 output, but to the SIG OUT pin. My confusion is related to how a 6.98k resistor between LEV1 and LEV2 was chosen to get an excitation voltage of around 3.5 Vrms, when the graph from the datasheet says that a resistance of 6.98k between LEV1 and LEV2 relates to a 5 Vrms output on the EXC1 and EXC2 pins.

Best regards,
Michael

Hello,

The board came in today and we measured the excitation voltage on pin 1 and pin 5. It was around 5 Vrms, which is the correct value from the datasheet. Thank you for your help.

Best regards,
Michael

Hi Michael,

Thank you for the clarification. You are correct, I have confirmed that the 0V to 5V mentioned in the documentation does refer to the signal output of the AD698

Thankws and regards,
Andy