AnsweredAssumed Answered

VND7140AJ-E Max current

Question asked by van_der_breggen.mich on Jun 8, 2016
Latest reply on Feb 8, 2017 by F G
Hello All,
i have a question about the VND7140AJ-E which i have incorperated into a design of our company. I read the datasheet several times, because the maximum current of the chip is not really stated as such, just as "internally limited". So i checked the Iliml and Ilimh parameters and they stated 4Atyp and 12Atyp. I need 4A max, so this should be more than enough for my application. 

The chip also has a maximum voltage of 28V which is enough for my 24V usage. We assembled the boards and I put it on the testbench. But to my surprise i can't get more than 1Amp out of it. I have been trying to figure out what is wrong, so I took off all the components which are around the VND7140 and i put the dutycycle on the input to 100%. Still just 1A.

Another thing i noticed while the VND7140 was on the board is that when i lowered the dutycycle it would go on for a second and then drop into failure mode. I thought this could be due to the fact that it measures a low voltage on the output, which is due to a set of capacitors used to change the PWM signal into analog DC. Which is strange since the datasheet doesn't state such protection and there is no more then 1A being drawn from the powersupply. 

I measured the output current which a constant current load. 

Does anybody have any ideas why this behaviour is being displayed and most of all how to get the current i really need.

With regards,
Michel van der Breggen

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