Products Mentioned

MAX25431 Production
The MAX25431 is a current-mode buck-boost controller. The device operates with input voltages from 6V to 36V. The switching frequency is resistor programmable...
Datasheet
MAX25431 on Analog.com

LTC3789 Recommended for New Designs
The LTC3789 is a high performance buck-boost switching regulator controller that operates from input voltages above, below or equal to the output voltage...
Datasheet
LTC3789 on Analog.com

MAX20048 Production
The MAX20048 is a current‐mode buck‐boost controller. The device operates with input voltages from 4.5V to 36V while using only 55µA quiescent current...
MAX20048 on Analog.com

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CSN1, CSP1 what are their maximum voltages?

		
	
				

			

									
					    andrew-lohmann@home
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Dec 20, 2025 
				
			
			
		
    
		
		                    	    
    
        	    
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                The user inquired about the voltage ratings for LX1, CSN1, and CSP1 in the absence of a VIN pin, with the IN pin supplying 5V initially and rising to 7 or 14V. The final answer clarifies that CSP1 and CSN1 must be below VIN, and the EN enable pin should be pulled low to reduce current draw from the output (a car battery). The accompanying answers confirm that Vin is equivalent to IN, and simulations with LTSpice models of LTM4712 and LTC3789 show a high current draw during start-up, while MAX20048 does not have this issue.
                        	    
    
                
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    Category: Datasheet/Specs
    
    		        		            		    
    Product Number:  MAX20048 
    
    		        		    		    
    
		    		    
		    			
    
			    
    LX1, CSN1 and CSP1 are rated at 0V -0.3V to Vin +0.3V, but there is no such pin as VIN.  There is an "IN" pin which I supply with 5V so that the IC can start up, it then rises to 7 or 14V when the output comes up.  The input at CSN1, CSP1 and MOSFET D is up to runs from 400mV to 35V.

    

    MAX25431 has the same ambiguity in the datasheet, but LTC3789 does not.
    

    An Engineers Perspective: Vintage and Veteran Car dynamo power management
    
			
    
			
									    
    
			        
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    				List two other ADI parts one also has the same ambiguity, the other datasheet is clear.
    
[edited by: andrew-lohmann@home at 5:45 PM (GMT -5) on 20 Dec 2025]
				
    
						
		                             
                        

    
    
                                            
                 Datasheet/Specs
                
                                                    
                 External Power Switch Buck-Boost Controllers
                
                                                    
                 MAX20048
                
                                                    
                 buck boost
                
                                                    
                 Buck-Boost Regulators
                
                                
            
    
    
    
		
    

				
				        
        		
    
			
						
									
												
			
			
                        
                                    
                        
                                                                    
                        
            
			            
						
						
			
			
			
			
		
    

        
        
        
    
					
    
			
    


    
















    
	
    
	
    
					



			


				
	









	
      
	

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                on Dec 26, 2025 11:23 AM
            
            
						
			            		
        
		
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        Using the LTSpice model suggests that Vin is the same as IN.  That is, with CS_ power the low voltage section if they are at the highest voltage.  Once that is dealt with, the IC works well in the model.
        

        By comparison with LTM4712 and LTC3789 LTSpice models demonstrate 
        a short period of very high current drawn during the start-up time for about 500uS, even with just 300mV input.  MAX20048 do not have this issue, though SiMetrix model could not run long enough to fully test it.  But all three simulations work, with a 100mV to start with power source.  
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

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                on Jan 15, 2026 8:03 AM
            
            
						
			            		
          
		
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          LTSpice show me that CSP1 and CSN1 must be below VIN.  EN enable must be pulled low to reduce current drawn from the output (a car battery).
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
				
						
				
				
				
		
		
          
			
		
          
	
          

          

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