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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 Jino,

    2. Actually, our ADC is AD9633. I just want us discussing based on same part ^0^. For the filter prior to ADC, the inductors&capacitors, can i use the same values? Or i have to caulculate according some formula to get the values? Also, you said the impedence between ADA4930 and AD9633 using 33 ohms, why not 50 ohms? Is the filter will add impedence to the path? Figure 60 doesn't add any resistors between driver and ADC, how to understand the difference between figure 59 and figure 60 about this?

    3. Closed,^0^.

    4. There are some difficults for me to undertand this so quickly, i'm not a analog engineer, however, i want to process ADC's output data. So i am the board design ower, i have to take those analog knowledges which i have given back to my teacher. I'll read the App note carefully. So it's back to the primary question, because i'm not confident about the driver circuit, can i just design my driver circuit refer to figure 60. Just replace the AD9640 by AD9633, and keep the same resistors configurations of the ADA4930. Our input source also is 1V p-p single ended, and make good 50 ohms impedence match in front designs. The Vocm will connect to AD9633's Vcm pin (which output 900 mV). Also ADA4930-2 will use single 3.3V power supply.

    For AD8001 issues, i'll create another thread.

    PS: I create new thread here:https://ez.analog.com/message/284446 , if possible, please help to take a look.

    Best regard.

Reply
  • Hi Jino,

    2. Actually, our ADC is AD9633. I just want us discussing based on same part ^0^. For the filter prior to ADC, the inductors&capacitors, can i use the same values? Or i have to caulculate according some formula to get the values? Also, you said the impedence between ADA4930 and AD9633 using 33 ohms, why not 50 ohms? Is the filter will add impedence to the path? Figure 60 doesn't add any resistors between driver and ADC, how to understand the difference between figure 59 and figure 60 about this?

    3. Closed,^0^.

    4. There are some difficults for me to undertand this so quickly, i'm not a analog engineer, however, i want to process ADC's output data. So i am the board design ower, i have to take those analog knowledges which i have given back to my teacher. I'll read the App note carefully. So it's back to the primary question, because i'm not confident about the driver circuit, can i just design my driver circuit refer to figure 60. Just replace the AD9640 by AD9633, and keep the same resistors configurations of the ADA4930. Our input source also is 1V p-p single ended, and make good 50 ohms impedence match in front designs. The Vocm will connect to AD9633's Vcm pin (which output 900 mV). Also ADA4930-2 will use single 3.3V power supply.

    For AD8001 issues, i'll create another thread.

    PS: I create new thread here:https://ez.analog.com/message/284446 , if possible, please help to take a look.

    Best regard.

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