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LTC7001 Recommended for New Designs
The LTC7001 is a fast high side N-channel MOSFET gate driver that operates from input voltages up to 135V. It contains an internal charge pump that fully...
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LTC7001 on Analog.com

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LTC7001 : Unable to turn on Load a second time.

		
	
				

			

									
					    Tuck
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Apr 30, 2026 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
    
		      		            		        
    Category: Hardware
    
    		        		            		    
    Product Number:  LTC7001  
    
    		        		    		    
    
		    		    
		    			
    
			    
    Hi ADI Team,
    

    I am using the LTC7001 device to control a Power Amplifier (PA). The circuit diagram is below (close to the Reference Board). Here are some parameters I used.
    

      

    • The input voltage to the PA is 28V (via a high side, low RDS_ON switch). 
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    • The control voltage (INP) is 3.3V
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    • VCC is set to 12V
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    • OVLO is configured to exceed 1.21V using a resistive divider and clamped with a 5.1V Zener for protection. If the input voltage to the PA exceeds 30V, the overvoltage protection will trigger.
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    When I test the circuit using a 10kOhm load in parallel with a 100uF capacitor, the circuit works as expected. I can turn it on and off, and the overvoltage level is correct.
    

    However, when I use a real Power Amplifier (3A current consumption), I find that I can only turn it on once. Subsequent enable signals on the INP pin is ignored.
    

    I later found that if I set the OVLO divider to trigger at 31V, then it is fine. 
    

    It appears that something has "latched up" the OVLO circuit of the LTC7001 after the first enable signal.
    

    Can I ask what I can do besides raising the overvoltage level to overcome this "internal latchup" ?
    

    Thanks.
    

     
    

    
			
    
			
									
		                             
                        

    
    
                                            
                 hardware
                
                                                    
                 MOSFET & Gate Drivers
                
                                                    
                 LTC7001
                
                                                    
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      •  Analog Employees  
      
            
						
                            
            
            				
            
                on May 6, 2026 6:26 AM
            
            
						
			            		
      
		
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      Hi,
       
      I think the problem is there is some energy storage in your PA. The problems you face seem to align with switching an inductive load. Which is different from the resistive + capacitive load where the switch driver works.  When driving a capacitive load, the switch turns off and the current in the PA decays to zero. The TS node and internal comparators (OVLO) sees a clean voltage and the driver is thus able the enalbe the load again. 

      A inductive load resists this change in current. When the high-side switch turns off, the stored energy in the PA forces current to continue flowing. To do so it means that the switch node Ts can momentarily goe below ground. This can happen even within spec. The fast transient the turning off creates disturbs the OVLO condition, making the driver “latched” until power cycled. 

      Raising the OVLO condition makes sure the OVLO threshold is not crossed, but this masks the issue. The datasheet of the LTC7001 recommends a TS to GND clamp diode when switching a inductive load. 
      “Optional Schottky Diode Usage on TS 
       
      When turning off a power MOSFET that is connected to an inductive component (inductor, long wire or complex load), the TS pin can be pulled below ground until the current in the inductive component has completely discharged. The TS pin is tolerant of voltages down to –6V, however, an optional Schottky diode with a voltage rating at least as high as the load voltage should be connected between TS and ground to prevent discharging the inductive through the TS pin of the LTC7001. See Figure 6” page 13 of the datasheet. 

      What is the application of the PA, are you using RF chokes, matching networks or other inductive elements? 

      Could you try to drive the same resistor with a inductor to see if the problem is there as well?

      Feel free to reach out if the problem keeps appearing even with the added diode. 
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
				
				
				
		
		
      
			
		
      
	
      

      

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                on May 6, 2026 7:21 AM
            
            
						
			            		
        
		
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        Hi ADI team,
        

        Yes, I do have a diode between TS and Ground. See the circuit diagram above. It is the diode D1 (ES1PD-M3/84A), I am following the LTC7001 EVB design example.
        

        There is some inductance, but the load is primarily a resistive load (high Quiescent DC current of ~3A). The RF PA is a sealed unit, so we do not have the circuit diagram of the components within.
        

        Any further thoughts or ideas ?
        

        Thanks.
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

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        •  Analog Employees  
        
            
						
                            
            
            				
            
                on May 6, 2026 11:11 AM
            
            
						
			            		
        
		
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        Are you using the eval kit DC2708A or the LTC7001 with your own components supporting?
        
			
        

		
			
	      

		
		
	
        
	
        
		
        
			
		
        
	
        
	
        
		
						
						
				
				
				
				
		
		
        
			
		
        
	
        

        

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                on May 6, 2026 11:19 AM
            
            
						
			            		
          
		
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          We designed our own board and circuit using the LTC7001, but closely following the schematic of the eval kit.
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
				
				
				
		
		
          
			
		
          
	
          

          

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          •  Analog Employees  
          
            
						
                            
            
            				
            
                on May 7, 2026 9:43 AM
            
            
						
			            		
          
		
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          Could you explain why you added a diode on the voltage divider on the OVLO pin? 
          
			
          

		
			
	      

		
		
	
          
	
          
		
          
			
		
          
	
          
	
          
		
						
						
				
				
				
				
		
		
          
			
		
          
	
          

          

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                on May 7, 2026 3:54 PM
            
            
						
			            		
            
		
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            Hi,
            

            I am following the suggestion on the Datasheet, Figure 2.
            

            It is there to keep the OVLO pin below the maximum rating of 6V.
            

            I have used a 5.1V Zener diode.
            
			
            

		
			
	      

		
		
	
            
	
            
		
            
			
		
            
	
            
	
            
		
						
						
				
				
				
				
		
		
            
			
		
            
	
            

            

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