LM3549: LED Driver with Lithium battery

Pavel Shkitun

Part Number: LM3549

Hi!

Datasheet says it's driver works with power 5.5 - 3.1 V.

Driver starts to work unstable and don't gives 350mA current (~120 mA extremely unstable current) when i take a battery as powersourse and voltage falls to 3.65.

Where i was wrong?

The power scheme was typical, as in the specification.

over 6 years ago

0 Kenneth Du over 6 years ago

TI__Genius 14295 points

Hi, Pavel,

Do you read Fault to see if there's any fault detected?

Also can you get the scopeshot including Vin/Vout/Iout?

Kenneth

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

Fault flag appears AFTER tripping the used channel. Flag of used channel.
As i said:

Vin = 4.2 - 3.65 V (Lithium Battery)
Vout = 2.847 V when Iout = 350 mA stable current.

Vin = 3.65 - 3.1 V
Vout = UNSTABLE (2.8+/-0.5) V when Iout = 120 mA UNSTABLE current. (350 mA were set)

I've tried to change I limit (15h), but it's not given me any result.

0 Kenneth Du over 6 years ago in reply to Pavel Shkitun

TI__Genius 14295 points

Hi, Pavel,

Can you use a DC supply to generate Vin = 3.65 - 3.1 V and see the result?

If it still happens, can you also check and show the current waveform of your inductor when the error happens?

Kenneth

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

LM3549 test.zip

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

Driver shutdown himself when Vin 3.49V.
Why?

0 Kenneth Du over 6 years ago in reply to Pavel Shkitun

TI__Genius 14295 points

Hi, Pavel,

Let me take a look at the result and also double confirm on our board.

In the same time, can you check to replace the IC to another one?

Kenneth

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

I've send you results earlier in zip archive.

Ok. I'll change the IC again.8272.LM3549 test.zip

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

I've changed the IC and saw the same picture.

Why?

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

Hi!

Have you any result with your board?

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

Hi!

What about my problem?

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

Hi!

It seems i've found a critical bug of your product.
If I've spent time identifying it, I deserve a reward. How do you think?
Can we discuss it by mail?
shkitun-pavel@yandex.ru

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

Why you couldn't answer me?

0 Kenneth Du over 6 years ago in reply to Pavel Shkitun

TI__Genius 14295 points

Hi, Pavel,

I checked on my EVM, but for Vin range from 3.1V to 5V, I don't see a problem.

Can you attach your schematic?

Thanks.
Kenneth

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

V_battery_Out connected to the lithium battery via connector.

Would you show me schematic of your testing plate and oscilloscopic pictures of V_out, L1 and L2 with 350mA current when V_in (VDDP, VDDS) = 3.4V-3.2V, please?

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

Will you help me with my problem or i should ask opinion of enother engineers in a web media?

0 Kenneth Du over 6 years ago in reply to Pavel Shkitun

TI__Genius 14295 points

Hi, Pavel,

Sorry for the delay.

I use the LM3549EVM, so you can find the schematic in the user guide:

Please find the test result:

The condition is Vin = 3.2V, the current is 350mA.

0 Kenneth Du over 6 years ago in reply to Kenneth Du

TI__Genius 14295 points

Hi, Pavel,

I'll close this thread due to inactivity and if you have more questions please reply to it directly and it will open again.

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

I think you didn't use a 3.2 V source. You didn't show a V_IN while driver working.
Also what is the register setting values were in driver?

0 Kenneth Du over 6 years ago in reply to Pavel Shkitun

TI__Genius 14295 points

Please see the following figures. Of cource I use 3.2V. I just didn't have an extra channel to show Vdd.

Are you able to contact TI local sales to help you?

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

I am convinced that someone's lying. If it wasn't you, it was the dealer. The layout and wiring were made exactly as recommended.

I'll talk with a dealer.

Thanks!

0 Pavel Shkitun over 6 years ago in reply to Kenneth Du

Prodigy 150 points

New information:

The devil seems to have been hidden in the pump inductance - the spread of the inductance operating frequency range can cause a lot of pain. You might want to increase the requirements for pump inductor.

Thanks for help!

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LM3549: LED Driver with Lithium battery