LM3414HV: current leakage with driver is in Off state

Gaston Schelotto

Part Number: LM3414HV

Hi,

I've successfully implemented a LM1434HV LED driver. However when the driver is in Off state the LED strings are slightly illuminated. Measured current is about 6uA (enough to slightly switch on them). How can avoid this issue? In other thread (with no TI answers) I've seen something like adding a 330k resistor in parallel with the LED strings. I have some doubts with this workaround. Above all, what happens with this resistance when driver switches to On state?

Could someone from TI clarify this?

Thanks in advace,
gaston

over 8 years ago

0 Vincenzo Pizzolante over 8 years ago

TI__Mastermind 25586 points

hi Gaston,

that's actually the trick, to add a dummy load / alternative path to the leakage current...
this is a common "problem" to all the floating drivers

KR
Vincenzo

0 Gaston Schelotto over 8 years ago in reply to Vincenzo Pizzolante

Expert 2860 points

Hi Vincenzo,

Thanks for clarify this. I assume that this alternative (high impedance) path is bypassed by the LED strings (low impedance) path when the driver is On, right?

regards,
gaston

0 Vincenzo Pizzolante over 8 years ago in reply to Gaston Schelotto

TI__Mastermind 25586 points

yes.

when the LED are on, they show a very little dinamic resistance so the big R in parallel is basically transparent / an open...
while when the LED are off, they show a very high dynamic resistance, so the big R in parallel becomes the preferred path...
you pick up a value based on the LED characteristics, typically tens/hundreds of KOhm is enough...
what is the LED you are using? which kind of string (xSyP)?

KR
Vincenzo

0 Gaston Schelotto over 8 years ago in reply to Vincenzo Pizzolante

Expert 2860 points

Hi Vincenzo,

I'm using a SPMWHT221MD5WAT0S0 Samsung (2.86Vf Typ @ 65mA) LED in a 7S3P configuration. I've measured a current of 5.6uA using a 300k resistor (driver Off) and a current of 30uA when driver is in On state. I think it's working very well and it solves the problem of illuminating LEDs when driver is in Off state. Many thanks for your help!

regards,
gaston

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LM3414HV: current leakage with driver is in Off state