AD9649-20EBZ : The power supply of U105 is different from the schematics(Rev.B)

Hello ,

Our customer purchaced 2-units of AD9649-20EBZ.

The customer saids that the LDO of U105 is different from schematic Rev.B .

ADP1706ARDZ-1.8 is mounted as U105, this LDO is a same as U104.

Both of t he 2-units are the same.

I have had the BOM list from AD9629-20EBZ BOM list 

In this list, the U105 is ADP1706-ARDZ-1.8-R7.

Does the schematics(Rev.B) is wrong ?

Best regards,


  • 0
    •  Analog Employees 
    on Jul 6, 2017 8:31 AM

    Hello Suzuki-san,

    As you have observed, U105 on the AD9649 evaluation board BOM does not match U105 in the schematic. I'm sorry about that.

    Here is my understanding of the situation. The BOM was changed (many years ago) so that U105 is the same as U104 (both 1.8V LDOs).

    U104 powers AD9649 DRVDD, which determines the logic levels of the SPI pins on the AD9649, in addition to setting the logic levels of the ADC digital outputs.

    U105 powers the SPI level shifters on the evaluation board, and sets the SPI logic levels on the board.

    To have the board SPI levels match the AD9649 SPI levels, the voltage from U104 and U105 must match. The board has been in production this way for several years, and works well.

    Is U105 being the 1.8V LDO causing your customer any problems?

    Again, I'm sorry about the discrepancy. I'll request the schematic to be changed, but I cannot guarantee how quickly that will happen.


  • Hello Doug-san,

    Thank you for your support.

    I understand the situation and I forwarded your answer to our customer.

    He needs to use 3.3V I/O because his FPGA use 3.3V I/O.

    He will customize the evaluation board to use 3.3V I/O.

    Thank you,