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noise with the LTM2884(a)



		

			

									
						pierrecharlier
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on May 25, 2022 
				
			
			
		


				
		

		    		    
		    
		    		            		        
Category: Hardware

    		        		            		    
Product Number:  LTM2884(a) 

    		        		    		    	
			
Hello, I have a design with the LTM2884(a) at 5V supply. It seem that at "high" current pulse (~200mA OUTPUT), it start to make some acoustic noise at the current pulse frequency (8Khz). I use 100µF capacitor at the output and 47µF input to reduce it but it's still noisy.


Any idea for reducing ?


Regards

								


				
				
		

			
						
									
									
						
						
			
			
			
			
		


					

			





	

		
	











	

	

					



			


				
	









	
    
	

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                                 Analog Employees 
                                
                            
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                on Jun 1, 2022 8:11 AM
            
            
					
    
	
    

		
		
    
					
    Hi Pierre,
    

    Sorry for the delay in responding. Could you please share some additional information about your circuit in order to understand what's happening here?
    

    How are VLO and VLO2 connected? With 5V input, 200 mA is the maximum downstream power available - can you confirm that no circuit downstream is attempting to draw >200 mA in this situation?
    

    It would also be helpful to share the relevant section of your schematic and layout (you could PM me with these).
    

    Best regards,
    

    Conal
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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                on Jun 1, 2022 10:06 AM
            
            
												
						in reply to ConalW
					
									
    
	
    

		
		
    
					
    Hello, thank you for the answer. I cannot measure directly the downstream current (board came fully assembled) but the system draw 350mA at upstream, so according to the 55% efficiency it should be ok I guess.
    

    

    Here is the input schematics, the system have a 100µF capacitor at output and a 10µF in  // with 1µF at input.
    

    So:
    

    VLO is connected to ON
    

    VLO2 is connected to nothing, following the DC1789A EVM schematics. 
     
    

    

    Regards,
    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
						
				
						
				
				
		
		
    
			
		
    
	
    

    

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