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ADN8834 Recommended for New Designs
The ADN88341 is a monolithic TEC controller with an integrated TEC controller. It has a linear power stage, a pulse-width modulation (PWM) power stage...
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ADN8834 on Analog.com

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ADN8834 Calc RC and RV for V and I limits of TEC



		

			

									
					    Optobru
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Feb 7, 2022 
				
			
			
		
    

				
		
    
		    		    
		    
		    	
			
    UG-858  has table 1 on page 3 to calculate RV1 and RV2, but sets abitraily RV2=10k which doen't work for most TECs.
    

    Similarly table 2 on page 4 shows RC1 and RC2 for pre-established current ratio.
    

    Equation for flexible V and I ratio shall be supplied and may look like:
    

    Say desired VTECMAXCool = 1.4V,  VTECMAXHeat=1.0V
    

    Because of the Avlim=2V/V, one finds
    

    VLIMcool= 0.7V and VLIMheat=0.5V
    

    Since Isink_Vlim = 10uA, one can find
    

    RVp = RV1||RV2  =  (VLIMcool - VLIMheat)/Isink_Vlim =  (0.7-0.5)/10u =  20kohms
    

    also
    

    Vratio=RV1/Rv2=(Vref-Vrv1)/rv1=1.8V/0.7V=2.57
    

    Then one can calculate
    

    RV1 = RVp * (1+ Vratio) = 71.4 kohms
    

    RV2 = RVp * (1 + 1/Vratio) = 27.8 koms
    

    

    

    Same principle can be applied for RC1 and RC2  where the Isink_Ilim=40uA. 
    

    

    

    

    
										

    
				Corrected with Vratio
    
[edited by: Optobru at 7:41 PM (GMT -5) on 7 Feb 2022]
				
    
					
    

				
				
		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	















    
	
    
	
    
					



			


				
	









	
      
	

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      •  Analog Employees  
      
            
			                            
                        
                on Feb 8, 2022 8:58 AM
            
            
					
      
	
      

		
		
      
					
      Hi Optobru,
      

      Thanks for posting here. 
      Yes, the table in the user guide suggest values of the resistor divider that gives TEC voltage limit that has same magnitude for cooling and heating. This is for easy suggesting values for the users. This may not work at all times for customer who wants different magnitude of TEC voltage limit but this table is beneficial to others. They can always go back to the equation you used to compute for the resistors if they want to use different magnitude of voltage limit at each mode. Same with the current limit. 
      

      I really find this suggestion of yours helpful. This really simplifies using the series of equation for computing the resistor values. I also checked your derived formula and find it correct. Thank you so much for this input.

      Regards,
      

      Noel
      
			
      

		
		
		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

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