LM3414HV off current (6uA) too high for application. HELP!! ;)

David Hillstrom

Other Parts Discussed in Thread: LM3414HV

I have a little problem with a circuit that I have inherited. I have included a .zip with two jpg's that outline the problem precisely. But it boils down to the fact that when the LM3414HV is "shut down" with a low on the DIM pin, the thing still draws about 6uA through the LEDs, which is way too much for my application. I am not really a power guy, and more of a control designer, so I am a little lost on this one, and I need to get a prototype out reasonably soon. I am open to workarounds or different topologies, as this is going to be a high volume product, with 6 to 12 circuits per unit, and unit volumes around 100K/yr by 2015.

HELP!!! ;)

(feel free to contact me.)

thanks,

-Dave

Driver Board Current Troubles.zip

over 13 years ago

0 David Hillstrom over 13 years ago

Prodigy 50 points

<tap><tap> anybody home? ;)

0 Jonathan Arzadon over 13 years ago in reply to David Hillstrom

TI__Intellectual 1825 points

Hello David,

Sorry for the delay in our response. We are currently trying to contact the right person who can assist you with the design. My hope is that we will be able to find the correct person who can help you solve your problem within the next day or so. Thank you for your patience.

Regards,

Jonathan Arzadon

0 David Hillstrom over 13 years ago in reply to Jonathan Arzadon

Prodigy 50 points

Jonathan,

That sounds great to me! I don't mind if it takes a little time, as long as I know someone is going to help. :)

- Dave Hillstrom

0 David Hillstrom over 13 years ago in reply to Jonathan Arzadon

Prodigy 50 points

Hi Jonathon,

It has been a week and I was wondering if there has been any progress made on my issue. Have you found the right person yet?

- Dave

0 Jonathan Arzadon over 13 years ago in reply to David Hillstrom

TI__Intellectual 1825 points

Hi Dave,

Sorry, I'm still waiting to hear back from some people. I'll poke them today and try to get a quick response. Hopefully, I'll be able to get back to you later today with some assistance.

Regards,

Jonathan

0 Jonathan Arzadon over 13 years ago in reply to Jonathan Arzadon

TI__Intellectual 1825 points

Hi Dave,

I was able to get a hold of one of the Application Engineers in the lighting group and this was his response to your design issue:

"This is spec’d in the DS (6uA). There will always be some amount of leakage current through any switch (FET) under bias even when it is off. With 6uA they simply need to put a resistor across the LED load to dissipate this low level during the off state. It will not amount to any appreciable efficiency decrease since the current is so small."

Does this solve your issue?

Regards,

Jonathan

0 David Hillstrom over 13 years ago in reply to Jonathan Arzadon

Prodigy 50 points

Jonathon,

That works great! 100Kohm resistor across the LED string shuts them off completely, not even a nanoamp, and reduces the on state output by only 0.05%. That's so simple I could just kick myself for not seeing it. heh

Thank you very much. :)

- Dave Hillstrom

0 Jonathan Arzadon over 13 years ago in reply to David Hillstrom

TI__Intellectual 1825 points

Dave,

Glad it worked out! If you have any other questions or comments, let me know.

Regards,

Jonathan

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LM3414HV off current (6uA) too high for application. HELP!! ;)