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LTC2996 Production
The LTC2996 is a high accuracy temperature sensor with adjustable overtemperature and undertemperature thresholds and open drain alert outputs. It converts...
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LTC2996 on Analog.com

LTC3351 Recommended for New Designs
The LTC3351 is a backup power controller that charges and monitors a series stack of one to four supercapacitors. The LTC3351’s synchronous step-down...
Datasheet
LTC3351 on Analog.com

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LTC2996 OV and UV Pull-up tolerance

		
	
				

			

									
					    Wayne E.
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jun 24, 2020 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    I would like to know what the tolerances are for the internal 400K pull-ups on the of OT and UT pins of the LTC2996. 
    

    I would like to tie these pins to the over-voltage pin of the LTC3351 but the pull-ups will affect the resistor divider setting my over-voltage threshold.  If the tolerances of the pull-ups are small enough, I may be able to use this approach. 
    

    Also, the LTC2996 datasheet shows diodes in series with the pull-ups.  Can you provide me with any information on their forward voltage drop and tolerance? 
    

    

    Wayne
    
			
    
			
									
		                             
                        

    
    
                                            
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      •  Super User  
      
            
						
                            
            
            				
            
                on Jul 6, 2020 3:55 AM
            
            
						
			            		
      
		
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      Hi Wayne,
      

      Wayne E. said:
      I would like to tie these pins to the over-voltage pin of the LTC3351
      

      Please describe what functionality you want to achieve.

      - Maybe you've misinterpreted the function of the over-voltage pin of LTC3351?
      When you connect OT, UT to over-voltage pin this would mean that an active OT, UT would disable over-voltage funtionality
      

      - internal pull-ups normally have horrible precision and temperature coefficient. So it would be advisable to place a p-channel mosfet
      in parallel from LTC3351 Vin (source) to UV (drain). Then you can connect OT and UT to gate.
      This would shut off LTC3351 when OT or UT is low.
      Maybe this helps.

      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Super User  
      
            
						
                            
            
            				
            
                on Jul 6, 2020 9:01 AM
            
            
												
						in reply to Alexxx
					
										
			            		
      
		
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      ...Sorry, I made a mistake:
      

      Alexxx said:
      So it would be advisable to place a p-channel mosfet
      in parallel from LTC3351 Vin (source) to UV (drain).
      

      Correctly: "From LTC3351 Vin (source) to OV (drain)".
      So the PMOS would simulate an overvoltage condition that shuts off of the LTC3351.
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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                on Jul 6, 2020 12:45 PM
            
            
												
						in reply to Alexxx
					
										
			            		
        
		
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        Thank you for your answer.  I will move forward with the p-channel MOSFET option.  
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
						
				
				
		
		
        
			
		
        
	
        

        

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