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LT3085 Recommended for New Designs
The LT3085 is a 500mA low dropout linear regulator that can be paralleled to increase output current or spread heat on surface mounted boards. Designed...
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LT3085 on Analog.com

AD5272 Production
The AD5272 / AD5274 are single-channel, 1024-/256-position digital rheostats that combine industry leading variable resistor performance with nonvolatile...
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AD5272 on Analog.com

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LT3085 as adjustable current source

		
	
				

			

									
					    tatery
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Mar 26, 2019 
				
			
			
		
    
		
		                    	    
    
        	    
    Thread Summary
    
                The user is experiencing issues with the LT3085 not functioning as an adjustable current source when using the AD5272-100 digital potentiometer. The final answer suggests potential stability issues due to capacitance at the A and W pins of the AD5272, recommending either interchanging the terminal connected to the set pin or following a specific current source configuration. The user confirmed that a common variable resistor works correctly and that the AD5272 resistance changes as expected, but the issue persists.
                        	    
    
                
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    Hello,
    

    I'm trying to use LT3085 as adjustable current source. From application note it seems to be very easy:
    

     
    

    My design is as follows:
    

     
    

    AD5272-100 is 100k Ohm resistor controlled through i2c interface.
    

    I have two issues:
    

    1. Output current is not adjustable. It means that current is not changing if I change resistance of AD5272 (for 0Ohm or 100kOhm output current is the same)
    

    2. Changing load in range 2-100Ohm cause that voltage on output is keep stable (~2V) but current is changing so it does not work as current source but as voltage source
    

    Could you please help me with understanding what is wrong here?
    
			
    
			
									
		                             
                        

    
    
                                            
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