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					    IngTasco
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Apr 28, 2025 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  EVAL-CN0359 
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hello everyone. I've reviewed the schematic files for the EVAL-CN0359 board and have already purchased some components to assemble a prototype I want to develop. I have some questions regarding this design and would like to know if you can help clarify them:
    

    * When the +Vexc signal is generated, I see that a Digital Analog Output (DAC) is used. Does this signal only generate 1.2V (constant) or does it have another function?
    

    * I would like to know the PWM frequency of the PWM0, PWM1, and PWM2 outputs, their duty cycle, and if these frequencies are fixed.
    

    Thank you very much.
    

    I hope you can help me.
    

    

    

    Alvaro Tasco
    
			
    
			
									
		                             
                        

    
    
                                            
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                 EVAL-CN0359
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on May 1, 2025 8:29 PM
            
            
						
			            		
      
		
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      Hi  ,
      

      You may refer to the CN-0359 (Rev. C) Circuit Note document for more details about the CN0359 reference design as well as the CN0359 Conductivity Measurement System User Guide [Analog Devices Wiki] to navigate through the available CN0359 examples.
      

      Please see the responses to your questions:
      

      1.  
      

      The +VEXC and -VEXC voltages are generated by the ADA4077 op-amp. The amplitude of the excitation voltage is controlled by the DAC output of the ADuCM360. The ADA4077 op-amp has a closed-loop gain of 8.33 which then converts the DAC output (0V to 1.2V) to the +VEXC voltage of 0V to 10V. For example, generating a max DAC voltage of 1.2V produces approx. 10V excitation voltage (1.2V * 8.33 = 10V). The second ADA4077 is then used to invert the +VEXC to generate the -VEXC voltage.
      

      For your reference, in the CN0359 User Guide (CN0359 Conductivity Measurement System User Guide [Analog Devices Wiki]):
      

      - The setvolt (Set Excitation Voltage) command is used to set the peak voltage of the cell excitation signal, ranging from 0.1 V to 10V. You may refer to the CN0359 source code.
      

      Therefore, the DAC output voltage is varied using software between 0V - 1.2V, depending on your desired excitation voltage.
      

      * More details at the EXCITATION GENERATION section of the CN0359 Circuit Note: CN-0359 (Rev. C)
      

      

      2. The ADuCM360 generates the PWM0 square wave switching signal for the ADG1419 switch, as well as PWM1 and PWM2 synchronizing signals for the synchronous sampling stages. All of these PWM signals are software configurable. You may refer to the CN0359 source code. 
      

      For your reference, in the CN0359 User Guide (CN0359 Conductivity Measurement System User Guide [Analog Devices Wiki]):
      

      - The setfreq (Set Excitation Frequency) command is used to set the frequency of the cell excitation signal, ranging from 10 Hz to 100000 Hz.
      

      - The sethtm (Set Track-And-Hold Hold Time) command is used to set the track-and-hold hold time as a percentage of a half excitation period, ranging from 0% to 10%.
      

      Regards,
      Andy
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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