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LTM4676A CHANNEL 1 DOESN'T WORK!



		

			

									
						asadi.siyavash
					
							

			
				
									
											
							 		
		        	            							
			
			    	
			                    
                
				                on Feb 11, 2019 
				
			
			
		


				
		

		    		    
		    
		    	
			
Hello,


I designed my board with LTM4676A but I faced with very unknown problems.


The parameters of my design is:


V input = 12V


RUN 0=3.3V


RUN 1=3.3V


V out CH0 = 3.75V (Rout0cfg=32.4K , Rtrim0cfg=2.43K)


V out CH1= 3.75V (Rout1cfg=32.4K , Rtrim1cfg=2.43K)


both channel's output is open (NO LOAD).


what happened: 


we had 2 similar board which we had similar problem in both. I set Vout with the help of Table 2 (Pin strapping look up table) of datasheet. when I test the voltage of channels I found that channel 0 set correctly but the channel one was not correct! channel 1 instead of having 3.75V DC voltage its out put is a pulse that mean fault occurred, as picture below shown.


Channel 0 Voutchannel 1 Vout


left picture is channel 0 Vout and right picture is Channel 1. (please consider our oscilloscope has a bit offset so it shown 3.62V instead of 3.75)


also I checked SW0 and SW1. the result is:


sw0sw1 


the left side is SW0 and right side is SW1.


Also we checked register of LTM4676A with the help of I2C. First of all we didn't have any error when reading channel 0 but we faced with many errors in channel 1.


the result for channel 1 was:


STAUS_BYTE=0x61


STATUS_VOUT= 0xD0


please consider both output are no load.


Also the schematic attached.




Any help would greatly appreciated.


Sincerely yours,


Siyavash


LTM4676A.pdf