Products Mentioned

AD9653 Recommended for New Designs
The AD9653 is a quad, 16-bit, 125 MSPS analog-to-digital converter (ADC) with an on-chip sample-and-hold circuit designed for low cost, low power, small...
Datasheet
AD9653 on Analog.com

AD9655 Recommended for New Designs
The AD9655 is a dual, 16-bit, 125 MSPS analog-to-digital converter (ADC) with an on-chip sample-and-hold circuit designed for low cost, low power, small...
Datasheet
AD9655 on Analog.com

AD9461 Production
The AD9461 is a 16-bit, monolithic, sampling analog-to-digital converter (ADC) with an on-chip track-and-hold circuit. It is optimized for performance...
Datasheet
AD9461 on Analog.com

LTC2195 Production
The LTC2195/LTC2194/LTC2193 are 2-channel, simultaneous sampling 16-bit A/D converters designed for digitizing high frequency, wide dynamic range signals...
Datasheet
LTC2195 on Analog.com

LTC2107 Production
The LTC2107 is a 16-bit, 210Msps high performance ADC. The combination of high sample rate, low noise and high linearity enable a new generation of digital...
Datasheet
LTC2107 on Analog.com

ad9652 Recommended for New Designs
The AD9652 is a dual, 16-bit analog-to-digital converter (ADC) with sampling speeds of up to 310 MSPS. It is designed to support demanding, high speed...
Datasheet
ad9652 on Analog.com

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how do I know if an ADC is suitable for IF sampling, i.e AD9653 or AD9655?

		
	
				

			

									
					    rwe
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Dec 5, 2018 
				
			
			
		

		
		                     
				
        		

		    
		    		    
		    			

			    
I have some question on determining the IF sampling capability of ADC's :


I've checked the ADCs selection table for ADC > 10MSPS


    

  • some ADC datasheets explicitly mention that the device is suitable for IF sampling, i.e : AD9461, LTC2195, ...
    • 

  • some ADC dasheets also specify the max IF frequency, i.e. AD9268-125 says 'up to 300MHz', LTC2107 says 'up to 500MHz'
    • 

  • some ADC datasheets even give specs, i.e. AD9652 contains plenty of specs for Nyquist 1, 2 an 3 zones
    • 

  • some ADC datasheets don't mention IF sampling at all, i.e. AD9653 and AD9655
    • 



now I'm interested in these last 2 devices, because of their low-power and low-pin count. But I'm not sure if these are suitable for IF sampling. I'm not a high-speed ADC expert, so can anyone explain me what paramaters I need to check to know if the ADC is suitable or not for IF sampling? I guess the full power analog bandwidth and the sample and hold-time are important, but some explanation would really be appreciated!

			

			
									
		                             
                        

    

                                            
                 ad9653
                
                                                    
                 ad9461
                
                                                    
                 LTC2195
                
                                                    
                 LTC2107
                
                                                    
                 High Speed A/D Converters >10 MSPS
                
                                        
                                            
                
                
                                        
                                            
                
                
                                        
                                            
                
                
                                
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                on Dec 5, 2018 8:09 AM
            
            
						
			            		
    
		
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    Hi 
    

    I completely can understand where you are coming from here. I apologize for the various "standards" and language used in these datasheets. Ultimately, the IF performance comes down to 
    

    - how much is the analog input (or -3dB) bandwidth of the sampler
    

    - how much jitter is in the system that could limit performance
    

    If you start to compare the two parts, we can compare the -3dB BW and Aperture jitter, for starters
    

    

    Part #        |  -3dB BW (MHz)         |  Aperture jitter (fs_rms)
    

    

    AD9655     |  500                             | 80
    

    AD9653     |  650                             | 135
    

    

    I dont know the IF frequency range you plan to use. But I can infer two things
    

    - the AD9653 has higher -3dB BW. So you can undersample higher frequencies compared to the AD9655
    

    - however, the AD9653 also has higher jitter, which means the SNR degradation due to jitter will also be higher for AD9653 compared to AD9655
    

    

    This is evident in the SNR (dBFS) table below. All this information is derived from the datasheet. 
    

    Freq (MHz)      |  AD9655 (VREF = 1.4V)         |  AD9653 (VREF = 1.3V)
    

    

    9.7                   |  79.6                                        | 80.1
    

    200                  |  75                                           | 72.1
    

    300                  |  55                                           |  ? possibly much worse
    

    

    This shows that the AD9655 is clearly much better than the AD9653 when it comes to undersampling applications. However, if the performance is good enough for your application, please go ahead and choose the part that fits your needs. 
    

    Hope this helps answer your questions.
    

    Thanks
    

    Umesh
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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                on Dec 6, 2018 6:08 AM
            
            
												
						in reply to UmeshJ
					
										
			            		
    
		
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    UmeshJ said:
    - however, the AD9653 also has higher jitter, which means the SNR degradation due to jitter will also be higher for AD9653 compared to AD9655
    

    What is the effect of this jitter? What is the cause of the degraded SNR?
    

      

    • Does the amplitude decrease due to the change in the sinx/x curve, so related to the imperfect Dirac sampling?
      • 

    • Or will the noise be higher? Is there a noise contribution versus frequency?
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                on Dec 6, 2018 6:30 AM
            
            
												
						in reply to JV-IE
					
										
			            		
    
		
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    JV-IE said:
    What is the effect of this jitter? What is the cause of the degraded SNR?
    

    here is some information for you to peruse
    

    www.analog.com/an-756
    

    https://www.analog.com/media/en/training-seminars/tutorials/mt-007.pdf
    

    https://www.analog.com/media/en/training-seminars/tutorials/mt-008.pdf
    

    https://www.analog.com/en/analog-dialogue/articles/adc-modeling-tools-speed-up-eval.html
    

    the degradation in noise is an artifact of the jitter or uncertainty in the sampling window. 
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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