I have connected the ADS5263EVM to a Virtex-6 FPGA. Following Table-2 in SLAU344, I have set up the device to use all 4 channels in the transformer path for 16-bit ADC.
I have used the following configuration for Channel 1, and followed the table accordingly for the other 3 channels:
R80,R81 = Open ; R169,R170 = 0 Ω ; R35, R153 =Open
Although Section 2.3 suggests that the inputs will use the INxA SMA ports, I am only able to obtain a signal using the INxB ports.
Currently, I am able to capture a 1MHz input signal successfully, but I am unable to see any change in output when connecting a DC input signal.
In the ADS5263 GUI, I have enabled 16X serialization in 2-wire mode.
Is there something in the documentation that I have misunderstood or overlooked? Why am I unable to capture a DC change? And am I correct in using the INxB ports for my desired setup?
Thank you in advance for your help.
For setting up the 4-channles with 16bit and transformer, you should follow the schematic in SLAU344, page 32 and page 33.
There are two groups of SMA ports: Group A (J27, J28, J29, J30) drive the OPAMP inputs; Group B ( J14, J16, J17 and J19) drive the transformer inputs.
You have to make sure your input signals are fed into the correct SMA ports that drive directly the transformers: J14, J16, J17 and J19.
Please note the silk screen label "INxB", next to J14, J16, J17 and J19 input SMA ports, could be misleading, since we also call A and B the 16bit and 14 bit mode...
If you follow the schematic closely, you will see that what really sets the 16bit vs 14bit mode is the resistors configuration:
R35, R153, R154, R155, R165, R166, R167, R168 shall be OPEN;
R169, R170, R171, R172, R173, R174, R175, R176 shall be 0Ω;
Let me know if this solve the issue.
That information confirms that my board is setup correctly. The A/B labeling for different reasons is very confusing.
The only issue I am dealing with now is the DC blocking. I have tried the transformer and OPAMP paths and neither is able to detect a DC change in the input signal.
Thank you for your help,
concerning the input DC blocking: all inputs have DC blocking. Please see the EVM schematic (SLAU344 page 31..33)
The OPAMP inputs have 0.1uF DC blocking cap: C62, C90, C110, C118.
The input transformer would block the DC by definition. The transformers are Coilcraft WBC1-1TLB (http://www.coilcraft.com/wbc.cfm) and the bandwidth is 0.25MHz....750MHz.
So, none of the input will detect a change in the DC level.
Is it possible to modify the OPAMP path of the board in order to detect a DC change?
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