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BQ24295: BQ24295 Standalone and not use TS pin.

Chun Youngsu
Expert 2485 points
Part Number: BQ24295
Other Parts Discussed in Thread: BQ24296, BQ24297

HI. TI

I would like to check if the BQ24295 product supports Standalone MODE.

And I want to know how to design a way to not use RTH on TS pin.

The SPEC we want is shown below.
VIN: 5V
Charging current and output: 2A
Output voltage: 6V
Charging voltage: 4.2V (Li-Ion)

I will wait for your reply.

Thanks.








								


				
				

				
			

		

			
						
									
                			    			                        
						
						
			
			
						
			                        
			
			
				
			  
			

			     
			

		


				    			

						
















	

	

					
    
	
    





		
	
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                          TI__Mastermind
                        25800 points
                      
    
                          
                   		
		
    
					
    Hey Chun,
    

    
There a couple things here that I would like to clarify before I start recommending application decisions for the bq24295:
    

    
1) You want your output voltage to by 6V? Are you referring to the voltage at VSYS? Or is this the output of your adapter/supply?
    

    
2) What is an RTH? I am not familiar with that component type. Are you referring to a NTC (thermistor) that is typically used for TS?
    

    

    
In terms of TS pin, to disable the function in Standalone mode, you only need to provide a fixed voltage divider that falls within the normal range of operating temperatures. You essentially tell the charger there is temperature fault. I suggest using something like a 5k Ohm in series with a 7.5k Ohm to give you a ~60%REGN value at TS. 
    

    
Unfortunately, the bq24295 has a default charge current of 1A. You may want to look at the bq24296 or bq24297 series of parts from the same family which can also operate in Standalone and provide a default charge current of 2A.
    

    
The default charge regulation voltage is also 4.2V for the family of parts. 
    

    
Other things to consider are input current limits to your supply (i.e. a typical wall adapters can only provide 5V/2A), so you must consider how much power you can actually provide to the input, and whether you want the charger to limit the input current, or limit the drop on the input voltage. In regards to this, take a look at the datasheet and read about the ILIM pins function, and also section 8.3.2.2 Dynamic Power Management in the datasheet. 
    

    

    
Regards,
    
Joel H
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    

	            
                 	
	
    
				
		                
                
                
                
                
                
                
        		
		
				
    
			
		
    
		
		 
		
		
     
    
	
    

    
			
    
			
    
		
    

		
    
	
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