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LTM4619 Recommended for New Designs
The LTM4619 is a complete dual 4A or single 8A stepdown DC/DC µModule® (power module) regulator. Included in the package are the switching controller,...
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LTM4619 on Analog.com

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LTM4619 Potential Damage Comp Pin Loading

		
	
				

			

									
					    aramder
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 30, 2023 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  LTM4619 
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hello,
    

    I am having an issue with an LTM4619 on a board I'm bringing up. Unfortunately, the COMP pins had capacitors installed on them by mistake, as shown in the schematic. The device draws an acceptable quiescent current when VBUS is fed 12V and the RUN pins are held low. When the supply was enabled via the RUN pins, it consumed 143mA at 12V with the output jumper disconnected, dropping slowly as the device warmed up. The output was holding at 950mV as expected. I was hoping for a simple explanation like a short on the outputs, however, I confirmed that there were no shorts anywhere and that all components are approximately the expected value. Thermal imaging revealed nothing.

    After removing the COMP capacitors, the device exhibited the exact same behavior when powered and then enabled.
    

    I poked around in LTSpice to see if I could create a particularly stressful situation that might damage the part, but I don't think this has given much insight into a possible failure mode.
    

    My only thought at this point is that there may be a solder bridge under the LGA which was not not detected in fabrication/inspection.
    

    This coming week, I intend to look at a few things on a scope to see if that reveals anything. Any thoughts on the behavior so far would be appreciated.
    

    Thanks!
    

       
    

      
    
			
    
			
									
		                             
                        

    
    
                                            
                 hardware
                
                                                    
                 Compensation Network
                
                                                    
                 LTM4619
                
                                                    
                 Step-Down (Buck) Regulators
                
                                                    
                 Multiple Output Buck Regulators
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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                on Jul 31, 2023 1:48 PM
            
            
						
			            		
        
		
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        After inspecting some other serial numbers of this assembly, the COMP capacitors were also installed in other assemblies without any consequence. I assume that this points to a manufacturing flaw for some kind of short under the part on one of the control signals which I was not been able to detect in my initial troubleshooting.
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

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                on Aug 2, 2023 6:39 AM
            
            
						
			            		
          
		
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          Based on the information provided, it seems that you are experiencing some issues with the LTM4619 on your board. Here are a few thoughts and suggestions to consider:
          

          1. **Schematic Review**: Double-check the LTM4619's schematic to ensure that all connections are correct. Verify that the pin connections, especially for the COMP pins, are properly connected as per the datasheet recommendations.
          

          2. **Input Power Supply**: Confirm that the input power supply is within the recommended operating range for the LTM4619. Any deviation from the specified voltage range can affect the device's behavior.
          

          3. **Thermal Considerations**: Check the thermal management on your board. The LTM4619, like many power management devices, can generate heat during operation. Make sure that there is sufficient thermal dissipation to keep the device within its safe operating temperature range.
          

          4. **Output Load**: Make sure that the output load is within the LTM4619's specified range. Excessive load or short circuits on the output can lead to abnormal behavior.
          

          5. **Enable Pins and Sequencing**: Review the enable pins and ensure that the sequencing of power-on and power-off is correctly implemented. Incorrect sequencing can result in excessive current draw or instability.
          

          6. **Scope Analysis**: Using an oscilloscope, examine the waveforms on the input, output, and enable pins during startup and operation. Look for any anomalies or irregularities that might give insights into the problem.
          

          7. **Inspect Board and Soldering**: As you mentioned, carefully inspect the board for solder bridges, damaged traces, or any other potential manufacturing defects. Ensure that the LTM4619 is soldered correctly and that there are no soldering issues.  securitasepay.com
          

          8. **Component Quality**: Verify the quality and authenticity of the LTM4619 IC itself. Unfortunately, counterfeit or substandard components can cause unexpected behavior in electronic circuits.  Securitas ePay
          

          9. **Contact Manufacturer**: If you are still unable to identify the issue, consider reaching out to the manufacturer's technical support for assistance. They might have additional insights or could provide guidance on troubleshooting the specific issue you are facing.
          

          It's essential to follow standard troubleshooting practices and perform a systematic analysis of the circuit to identify the root cause. Sometimes, power-related issues can be complex, but with a methodical approach and collaboration with the manufacturer's support, you should be able to diagnose and resolve the problem effectively.
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
				
				
				
		
		
          
			
		
          
	
          

          

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