AnsweredAssumed Answered

AD5764R -1,4V Output Offset

Question asked by Sercan on Nov 20, 2017
Latest reply on Nov 21, 2017 by Sercan

Hi,

 

When I program AD5764R to give an output it gives an -1,4V offset.

  • This situation occurs at our 3 boards.
  • At one of these boards I also changed the DAC with a new one. But situation continues.

 

Below picture represents my schematic. DAC is driven directly by a Spartan6 fpga with 3,3V LVDS.

 

((Info: R51 was also tried as floating point. Offset situation continues.))

 

Can any one offer me what to check or what is the reason of this -1,4V offset please?

 

Please check my below steps:
((Dac-A & Dac-B readings we directly done over the DAC pins. (Pin 23 & 22 respectively.))

  • --- power up the IC.
    Dac-A = 0V
    Dac-B = 0V
    On the SDIN pin no signal came.

 

  • --- Send 0x010001 to program function register.
    Dac-A = 0V
    Dac-B = 0V
    On the SDIN pin 0x010001 signal was seen.
  • --- Send 0x1C0000
    Dac-A = -1,4V
    Dac-B = -1,4V
    On the SDIN pin 0x1C0000 signal was seen.
  • --- Send 0x240000
    Dac-A = -1,4V
    Dac-B = -1,4V
    On the SDIN pin 0x240000 signal was seen.
  • --- Send 0x2C0000
    Dac-A = -1,4V
    Dac-B = -1,4V
    On the SDIN pin 0x2C0000 signal was seen.

 

  • --- Send 0x110FFF
    Dac-A = -1,4V
    Dac-B = 0 V
  • --- Send 0x110000
    Dac-A = -1,4V
    Dac-B = -1,4V
  • --- Send 0x11FFFF
    Dac-A = -1,4V
    Dac-B = -1,4V
  • --- Send 0x11EEEE
    Dac-A = -1,4V
    Dac-B = -2,9V
  • --- Send 0x11DDDD
    Dac-A = -1,4V
    Dac-B = -4,3V
  • --- power down.

 

Best regards,

Sercan

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