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AD9912 Evaluation Board SysClk Input and USB connection

Question asked by br1anjtuck on Mar 17, 2014
Latest reply on Mar 24, 2014 by sitti



I have a stock (no alterations made) AD9912 PCBZ Rev B evaluation board, and I have two questions:


1). I want to drive the SYSCLK input with 1GHz external signal. The instructions in the data sheet indicate that a amplitude between 0dBm and +3dBm is fine to input, but I'm not sure whether or not there needs to be a DC offset applied to the 1GHz sinusoidal input signal that would ensure that no negative voltages enter the T5 transformer. Is the SYSCLK input sinusoidal signal supposed to have a DC offset applied to it and if so, what voltage would that offset need to be?


2). The USB connection is not working as the Eavluation Board Software says that it is not able to recognize the Evaluation Board and the red indicator light, "USB Status" on the board is not blinking like the data sheet should be.  However, the Software is initializing correctly, and I have all the proper power supplies hooked up to the board and it is seems that all the jumpers should be correct. My configuration matches the data sheet and is shown below:


- TB1 Connections are all hooked up to the correct supplies: VCC_USB,SIO_VDD,GND,DVDD,and AVDD

     -according to the datasheet, VDD_DACCLK and VDD_DRV/VDD_FDBK are supplied by the AVDD supply on TB1

- VDD_DACDEC is on 1.8 V supply.

- VDD_DAC3 and VDDX_DRV are on a 3.3 supply.


- JMP 4, 5, 6 and 7 are on VDD

- JMP 3 is on CONTROL

- JMP 2 in on

- JMP 8,9,10,11 are on

- All other jumper slots are empty.

- SYSCLK is being generated by a Signal Generator.


Is there something I am missing? Any ideas?