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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

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ltc1733 - CHRG pin

		
	
				

			

									
					    yinon@mmi.co.il
					
							

            
            			
				
									
											
			
			
				
			
			
			    	
			                    
                
				                on Jul 29, 2019 
				
			
			
		

		
		                     
				
        		

		    
		    		    
		    			

			    
Dear Support,


As I understand from the DS of LTC1733, and as I see it on our board, the CHRG pin become active and turn low as soon as Vcc is fully powered and the charge cycle start, even if the BAT pin is diconnected.


Am I correct?


Is there any kind of indication for BAT pin connection status?


BR,


Yinon

			

			
									
		                             
                        

    

                                            
                 battery charger ic
                
                                                    
                 Linear Battery Chargers
                
                                                    
                 LTC1733
                
                                
            

    
    
		


				
				        
        		

			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		


        
        
        
    
					

			





















	

	

					



			


				
	









	
    
	

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    •  Analog Employees  
    
            
						
                            
            
            				
            
                on Aug 9, 2019 4:11 PM
            
            
						
			            		
    
		
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    See datasheet, p.10, Table 1 for a description of the \CHRG pin.  If no battery is connected the LTC1733 will detect battery current < C/10 and go to 25µA pulldown state.  So, there is no difference between 1) Battery connected; battery is almost charged (charge current < C/10) and 2) battery disconnected.  In both cases if a capacitor is attached to TIMER the \CHRG pin will go to 25µA pulldown state until the timer times out.  If \CHRG pin is connected to ground, the \CHRG pin will go immediately to hi-z state. 
    

    Note that in "25µA pulldown" state, if you measure the voltage at \CHRG with no load (except Hi-Z input of DMM) you will see a logic-low state.  However, it is only a logic low for very light load.  You can't turn on an LED very well with 25µA.
    
			
    

		
			
	      

		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
						
				
				
				
		
		
    
			
		
    
	
    

    

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