Im using AD9744 DAC for one of my project and AD8047 for I_V converter for that DAC. Im getting output voltage twice the Input to adc fron AD8047.
Can anyone tell me how to connect onli one OUTA to AD8047.
The AD9744 converts input digital word to differential current outputs at IOUTA and IOUTB. These currents are converted to voltages across R410 & R411. This differential voltage is fed as input to differential amplifier AD8047.
The gain of the amplifier is decided by ratio (R404/R405. R409 = R404 and R406 = R405). At present it is 500E/225E = 2.2222, which is why you are getting doubled output. In case you need 1:1 output, you will have to replace R404, R405, R406 and R409 by equal value resistors.
The op amp output DAC2_VOUT is single ended with respect to analog ground.
Hope this helps.
Thank you jayan sir.
But im not able to work with higher frequency from 15MHz......I will find glitches for lower frequencies
Insufficient information. You have uploaded only one page out of 72 in your schematic. I'm sorry I cannot make any sense out of your description. JayantD
Find the attached schematics of ADC & DAC. The ADC data is taken to FPGA and driving to DAC input. ADC Clock is from PLL and Same clock is taken to FPGA and noted and provided for DAC.
From Signal generator im providing Annalog signal of 400mVpp because beyond that im not getting DAC output,because we are using the DAC interanal reference voltage.
Till 15MHz it is working fine with small glitches after that no proper output.
And one more can i have lower frequency from 1hz to 100Khz for the above interfacee.
I would suggest a step-by-step check with a scope, starting at the transformer secondary, then move on to the AD8352 input, its differential output, then AD9455 inputs. Once you are sure that there are no glitches on the input side, you can write test programs for generating known words at known frequencies, feeding these to AD9744 and probing through at each node, to the AD8047 output. If the hardware does not show any glitches for the test programs, then you will know for sure that the problem lies in your code. If there are glitches for the test programs as well, it could be a layout or component selection related issue.
Have you done signal integrity tests for your PCB layout?
Lower frequency response will solely depend on your RF Transformer characteristics. I doubt whether this will be feasible, though.
Hope this helps,
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