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Questions: When ADA4930 driving AD9633

1. The input common-mode voltage range of ADA4930-2 should be 0.3~2.8V. But, i found this parameter has different range in Chinese version datasheet, where is 0.3~1.2V. Also, there is same issue about output voltage range.

2. There are two blocks between ADA4930 and AD9633, which need me to make choices: one is the mach resistor, the DEV kit used 24 ohm, our previous board (between AD8138 and AD9218) used 50 ohm, there is no match resistor in figure 60 of ADA4930 datasheet, however 33ohm in figure 59; aonther is the RLC filter, is this necessary for my application? And  will the inductance destroy the DC coupling fucntion?

 

3.The DEV kit schamatic of the ADA4930 is same as figure 55 of the datasheet, so the ADA4930 was configured as G=1 and input 2Vpp, output also 2Vpp. My system, the front signal is 1Vpp, so i should refer to figure 60, am i right? Which convert the input 1Vpp to differential 2Vpp.

 

4, In dev kit, use Rcm(1.82K) pull-up to +3.3V. There also have several pull-down resistors. Can i remove these pull-down resistor in my design?

 

5. Can you teach me how to calculate each node's voltage based on figure 60 of ADA4930 datasheet? For, datasheet said "For a common-mode voltage of 1 V, each ADA4930-2 output swings between 0.501 V and 1.498 V, providing a 1.994 V p-p differential output. " I can understand how to get 1994 V p-p, but i don't know how to get 0.501 V and 1.498 V.

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  • Hi Coyoo,

    To enlighten you the major difference between figure 59 and 60, see the image below:

    Red Curve is figure 59 and Green is figure 60. To put it simply, the datasheet is for edit. Figure 60 should also include a 33 ohm for the filter network. If you will use AD9633 at 80 MSPS then use the same exact RLC values, otherwise calculate to match your desired filter response.

    Regards.

Reply
  • Hi Coyoo,

    To enlighten you the major difference between figure 59 and 60, see the image below:

    Red Curve is figure 59 and Green is figure 60. To put it simply, the datasheet is for edit. Figure 60 should also include a 33 ohm for the filter network. If you will use AD9633 at 80 MSPS then use the same exact RLC values, otherwise calculate to match your desired filter response.

    Regards.

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