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HMCAD1511/1520 input protection



		

			

									
						bruhaha
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Oct 23, 2019 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hi all,


HMCAD1511/1520 input should be in the range 0V-2V, with an absolute rating -0.3V-2-3V according to datasheet.


Is there any clamping achieved in chip, or should we implement it with discrete components? If so, do you have any advises schematic for it?


I haven't found any information related to this in the datasheet.


Best regards

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	














	

	

					



			


				
	









	
    
	

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                                 Analog Employees 
                                
                            
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                on Oct 23, 2019 9:21 PM
            
            
					
    
	
    

		
		
    
					
    Hi,
    

    Each Analog input is designed to accommodate an analog full scale swing of 1.0Vp-p around a fixed common mode voltage of 0.9V, or essentially a swing on each input between 0.4V to 1.4V. When both Ains are driven differentially this establishes the 2.0Vp-p "differential" Fullscale Input range.
    

    As noted in the AMR Table 1, the Abs max voltage rating for the Analog Inputs with respect to AVSS(Analog GND) are -0.3V to +2.3V. These AMR voltage levels are nearly a volt beyond the normal Ain operating levels of 0.4V to 1.4V.
    

    There are no inherent overvoltage protection circuits inside the Analog Inputs so the user must control the level of their Analog Input signal externally.
    

    Best Regards,
    

    TonyM
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
						
						
				
				
		
		
    
			
		
    
	
    

    

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                on Oct 24, 2019 8:18 AM
            
            
												
						in reply to ADIApproved
					
									
    
	
    

		
		
    
					
    Thanks TonyM for this clear and detailed explanation.
    

    Would you have any advice about the way we should implement such protection?
    

    We have the ADC input driven by a LT6600 driver, powered with +/-5V.
    

    We would like to be sure that the protection does not affect visibly our analog signal.
    

    Best regards
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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                                 Analog Employees 
                                
                            
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                on Nov 1, 2019 7:11 PM
            
            
												
						in reply to bruhaha
					
									
    
	
    

		
		
    
					
    Probably the easiest away to protect the input of the ADC would be to use protection diodes on the inputs tied to some clamp voltage.  They shouldn't distort the signals if they aren't conducting. 
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
						
				
				
		
		
    
			
		
    
	
    

    

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