Category: Hardware
Product Number: AD9635
My company would like to use an AD9635 driven by an ADA4930. The AD9635 evaluation board uses the ADA4930 for channel A, but the default BOM uses the passive path. I have not been able to find information on what board loading changes should be made to switch to the active path.
Here are my guesses and questions about enabling the active path:
- I would guess that most of the "DNI" components in the optional active path (bottom half of schematic sheet 5) should be added (C411, R424, L404, L406, C420, C421, L405, and L407).
- The note by those components says the values are place-holders. What is the recommended way to determine those values for our desired filter characteristics? (The desired characteristics are not yet know because the sampling rate has not been finally determined.)
- On the main input path, I would guess that R403, R404, C404, and C405 should be removed to disconnect the passive circuit, and R414 and R415 should be added to connect the active circuit.
- I found an EngineerZone post (AD9635 with ADA4927 as driver) that seems to indicate that R412, R410, R413, and C406 should also be removed, and I would guess that's right. To go with that, I would guess R424 should be added to connect VCM from the AD9635 to the ADA4930.
- Should we add the other DNI components in the top half of schematic sheet 5 (R416, C407, L403, C409, and C410)? If so, question 2 also applies to the values of these components, I think.
- A final question is about getting DC coupling the active path, which we need. Would shorting C411, C412, C417, C418, and C419 be the right way to do that? (That seems consistent with the example ADC driver circuits in the ADA4930 data sheet.)
Any assistance will be appreciated, especially for the questions in items 2 and 5.
Thanks,
Dan Alt
