Products Mentioned

LTC1733 Production
The LTC1733 is a standalone constant-current/constant-voltage linear charger for lithium-ion batteries with an on-chip power MOSFET. Internal thermal feedback...
Datasheet
LTC1733 on Analog.com

Thread Details

  • State Suggested Answer
  • Replies 2 replies
  • Answers 2 answers
  • Subscribers 39 subscribers
  • Views 626 views
  • Users 0 members are here 

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
LTC1733 - battery connection identification

		
	
				

			

									
					    yinon@mmi.co.il
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Jul 29, 2019 
				
			
			
		

		
		                     
				
        		

		    
		    		    
		    			

			    
Dear support,




As I understood according to the DS of the LTC1733, the CHRG pin becomes active (turn to 'low') as soon as there is power-in thru Vcc, meaning that the charge cycle started.


It means that if the battery is disconnected from BAT pin, it doesn't affect the CHRG pin.


I can also measure it on our board. When Vcc becomes 5v then CHRG pin become low, even when BAT pin is disconnected.


Is there any kind of indication which can indicate that the BAT pin is disconnected and the charge current is actually zero?




BR,


Yinon

			

			
									
		                             
                        

    

                                            
                 battery charger ic
                
                                                    
                 Linear Battery Chargers
                
                                                    
                 LTC1733
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			


				
	









	
    
	

  • 
	
    



	
			
		
	



    
	
    
		
    
							
					
    
		
    
		    
		    		    
			
				
									
							        
			
			
			
    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Aug 2, 2019 10:44 AM
            
            
						
			            		
    
		
										0
					
	
    

		
		
    
		
    
                                
                                                            
    
					
    The \CHRG pin should behave as described in p. 10 of the datasheet.  Less-than-C/10 charging current will cause the \CHRG pin to go high impedance or 25µA pull down (see p. 10 for detail).  (Note that the timer can be disabled by shorting TIMER to ground which should cause \CHRG to go hi-Z immediately upon reaching C/10 charge current.)  However, you will not be able to distinguish a fully charged battery and a disconnected battery since they both look the same to the LTC1733.
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
				
				
				
		
		
    
			
		
    
	
    

    

    • 

	

  • 
	
    



	
			
		
	



    
	
    
		
    
							
					
    
		
    
		    
		    		    
			
				
									
							        
			
			
			
    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Aug 2, 2019 10:53 AM
            
            
						
			            		
    
		
										0
					
	
    

		
		
    
		
    
                                
                                                            
    
					
    "I can also measure it on our board. When Vcc becomes 5v then CHRG pin become low, even when BAT pin is disconnected."
    

    

    If the battery is disconnected at power up, and the TIMER pin is not shorted to ground, the \CHRG pin should be '25µA pull down.  You will measure ~0V with a hi-input-impedance DMM.  However, I do not think you can turn on an LED with the current.  When the timer times out \CHRG will go to 'true' hi-Z.
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
				
				
				
		
		
    
			
		
    
	
    

    

    •