Hi all,
I've produced a PCB upon ADS1675REF original Protel SE Project.
To interface ADS1675 with my national instrument FPGA board i had to remove 100ohm resistors 'cause output swing was merely 2Vpp and removing those i actually have 3.3Vpp as required from national instruments Digital IO.
With 3.3V swing i can read out 24bits at almost all speed (@1MSPS i have some issues) but the digital output code is affected by huge noise, and just i cannot understand if it's FPGA that doesn't read every bit correctly or there is a real fluctuation in digital output code, but "magically" when i attach oscilloscope probe between DOUT and GND i can see how output code becomes considerably stabilized.
/DOUT and /SCLK are floating as datasheet suggests, and SCLK is connected to my FPGA board.
Can you suggest me which components may i add in output to stabilize the signal or digital word?
Also with no input i have a 5mV positive offset measured from ADC.. is there a way to compensate this? Can +9/-5 analog power supply be responsible for this due to the fact that +9/-4V were suggested to feed THS4503ID?
Thanks in advance.
MR