AD9554 eval board in "freerun" mode

Hi Hanoch,

Sorry for the delay. I just returned from vacation. The problem is most likely the result of the default evaluation board configuration. By default, the reference inputs are AC coupled for use with the self-biasing differential input receiver. The single-ended input receiver that you are using for your inputs is not self-biased. Provided the AC coupling capacitors and the bal-un are still installed on the evaluation board, the signal at the AD9554 reference input pins has a common mode voltage of 0 V. If that is the case, the input receiver will not see the high to low transitions of the reference clock. The simple way to remedy this is to use the differential input receiver format. However, with this format, the input signal should not exceed a 1.3V single-ended swing.

Neil,

thanks for your reply. Is there any way to re-work the eval board and drive with a single-ended signal? If yes, could you please provide me the re-work instructions?

Hi Hanoch,

For Ref A:

Remove: T201, R236, R261, C204

Populate:

R204 = 0 ohm resistor (underneath T201)

C204 = 0 ohm resistor

For Ref C:

Remove: T203, R243, R264, C211

Populate:

R222 = 0 ohm resistor (underneath T203)

C211 = 0 ohm resistor

The evaluation board schematics can be found on the product's evaluation page at analog.com and are at this direct link https://www.analog.com/media/en/technical-documentation/evaluation-documentation/AD9554_Evaluation_Schematic.pdf

Thanks Neil.

Working on the re-work. Will update you soon.

Hanoch