problems lm2678s-adj

Arturo Reta

I have one source co lm2678adj did a simulation to build according to the webench and assemble it shows me what the pcb does not work and the source is 18 to 27vdc with 13.8Vdc output with a current of 4 amp connect a load of. 5 amp and then connect a load works with 2.7 amp and voltage drops to 13.8 9.1vdc that is not what happens components are those of the list of materials and check the connections and position of components and are not correct because the voltage falls can you help?

over 10 years ago

0 Juan Paulo Fung over 10 years ago

TI__Expert 3870 points

Hi Arturo - Please send us a copy of your schematic, PCB layout and bill of materials for review. Is the device not starting at all? 0V at the output?

Best Regards,

-JP

0 Arturo Reta over 10 years ago in reply to Juan Paulo Fung

Prodigy 40 points

when I plug a .5 amp load no problem

but when 2.7 ampere low output voltage 9.1

0 Anston Lobo over 10 years ago in reply to Arturo Reta

TI__Genius 16025 points

Where are you measuring the output voltage? Across the load or across the regulator terminals?

Are you using a coupled inductor for your design? Also, your IC ground doesn't seem to be connected to board GND and Exposed Pad.

Thanks,
Anston

0 Arturo Reta over 10 years ago in reply to Anston Lobo

Prodigy 40 points

I was assembled according to diagram all voltages is measured at the output of the inductor where the load is connected

add the image of the pcb

thanks in advance

0 Anston Lobo over 10 years ago in reply to Arturo Reta

TI__Genius 16025 points

What is your input supply? Is is current limited in any way?
Also, check the diode rating to make sure it can handle 3A and is at least 40V.
Let me know if this works.

0 Anston Lobo over 10 years ago in reply to Anston Lobo

TI__Genius 16025 points

Also, Have you tried using a new regulator? Place an electrolytic capacitor on the input as well and check if this works.

0 Arturo Reta over 10 years ago in reply to Anston Lobo

Prodigy 40 points

perform a simulation in the WEBENCH and should work according to these parties because that's the list you gave me, the design is the same as giving me the WEBENCH and when tested with a load of 2.5amp not work, I see that these suggestions as an option they have not helped me, design is reference the original with their part numbers, leave it for a while but now I return to see if this reference design works or not but to change the design to another part number, there is someone who can answer me that question

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problems lm2678s-adj