Thread Details

  • State Suggested Answer
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 33 subscribers
  • Views 827 views
  • Users 0 members are here
Options
Related 

        

            Post
             Go back to editing
        

    

    


    

    









		


















	
	
			
	
			
		
	
	
		

	    
	    
	    		
LTC2662 Switch to V- mode

		
	
				

			

									
					    mthibs
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Nov 20, 2024 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  LTC2662  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hello,
    

    I am using the LTC2662 as a current source to drive a proportional solenoid valve, and here are a few questions I have.
    

    The coil resistance is 500 ohm, and the driving current is 10mA at full opening.
    

    I need to control the current direction in the coil, so is it a good idea to wire the load between OUT0 and OUT1 and use one output in "switch-to-V- mode", while V- is attached to ground ?
    In this way, to make the current flow in one direction, OUT1 is in “switch to V-” mode and OUT0 is the current source. And for the opposite direction, OUT0 is in “switch to V-” mode and OUT1 is the current source. See the schematic attached.
    

     
    

    

    Also, for convenience, I would like to use the LTC2672 with VDDx wired to a 5V supply. Unfortunately, that a bit too low to drive the 500ohm load at 10mA even with the low dropout output of this chip.
    Is there any circuit that I could add between DAC and load, such as a unity gain current amplifier with low input impedance and high load driving capability ?
    

    

    Thank you in advance for your help !
    Regards
    

    
			
    
			
									
		                             
                        

    
    
                                            
                 ltc2662
                
                                                    
                 ltc2672
                
                                                    
                 hardware
                
                                                    
                 Current Source-Sink D/A Converters
                
                                                    
                 Precision D/A Converters
                
                                        
                                            
                
                
                                
                    Show More
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                        
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

    • 
	
      



	
		
	
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Nov 24, 2024 8:13 PM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi  ,
      

       is currently taking a look at this query and will get back to you. Thanks for your patience.
      

      Br,
      

      Den
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Nov 25, 2024 8:24 PM
            
            
						
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi  
      

      I don't see an issue with the implementation you want to do. Just make sure be careful in setting the modes for each output pin. I suggest you default them to "switch to V-" first before setting the other to output a current. Sort of a break before make sequence, if that makes sense. Also you need to factor in the specs accompanying the switch to V- feature, if you look at table 2 from the datasheet, under DC performance you would see and impedance and a max DC current. 
      

      The current circuit you have should already work. You would need more than 5V due to drop out, to supply 10mA to a 500 ohm load. 
      

      You could use any op-amp as a buffer but you have to take into account if the output stage is able to sink 10mA with a only GND level at the negative supply. 
      

      Best regards,
      

      Ian
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

      • 

	

    • 
	
      



	
			
		
	



      
	
      
		
      
							
					
      
		
      
		    
		    		    
			
				
									
							        
			
			
			
      •  Analog Employees  
      
            
						
                            
            
            				
            
                on Dec 4, 2024 2:10 AM
            
            
												
						in reply to ADIApproved
					
										
			            		
      
		
										0
					
	
      

		
		
      
		
      
                                
                                                            
      
					
      Hi  
      

      Bidirectional currents can be generated using an IDAC and an Analog Switch. For the connections, you can refer to the attached diagrams . The IDAC provides a unidirectional positive current at its output, and the analog switch is responsible for changing the direction of the current in the load.
      

      For the solenoid value which is inductive in nature, you need a capacitor at the IDAC output to GND to slow down the transition for stability purposes.
      

      

       
      

       
      

      

      Regards
      

      Vikash
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
						
						
				
				
		
		
      
			
		
      
	
      

      

      •