MP24833-A Buck-Boost config. not working

Lighting Solutions
1

Hello Everybody!

I am trying to build a lantern with two MP24833A supplied with a 5S Battery.

Vin_min: 15V
Vin_max: 21V
I_max: 650mA
V_LED: 19,5V

Zwischenablage02
Zwischenablage021110×926 43.1 KB

But they let the magic smoke out after 1-2 seconds. Do I have an tremendous fault in my schematics? Or is the MP24833A not suited for this. The PWM dimming is done by a 3.3V MCU
If the MP24833 is not suited, is there another one? Minimal external parts and up to 3A Buck Boost LED driver?

Thanks for the help!

2

Hi Felix,

Welcome to the MPS Technical Forum!

Are the two MP24833-A used for two different systems/LED outputs?
Do both the devices have the same operating conditions? What is the switching frequency of the PWM dimming signal from the MCU?

3

Thanks for the fast reply.

Yes different LED-String, both identical.
Should be same operating conditions, same supply identical, but independent, LED-Strings.
ATmega 328p with 490Hz.

4

Hi Felix,

I think your schematic looks okay. Are you trying this on your proto board? Have you tried this circuit on our evaluation board?

Did you notice anything abnormal before the smoke out? Was the IC drawing high current? Did you get any waveforms before the smoke out?

5

Hello,
Tried this on the PCB I designed, since the schematic looked so easy, that I didn’t thought about using a proto board. And no didn’t use(bought) the evaluation board because of said reason, in hindsight a mistake.

High Current is relativ, it drew like 20% more current than anticipated 650-800mA. The IC lit the LED string up, sometimes 2-5 seconds and then bruned up. My oscilloscope is currently in repair after it was damaged, so I couldn’t observe the waveforms

6

Hi Felix,

Could you send us the layout file for this board?

Since the schematic looks correct, I think it would be good to check the layout for any errors.

7

Hello!
Thanks for your support.

If you want to have the Gerber Files, how can I send them to you?
The Board is fairly compact, since I need to work with existing constraints.

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22917×541 172 KB

8

Hi Felix,

Thank you for sharing your layout image. I will take a look at it and get back to you.

Did you try replacing the damaged IC with a new one on the same board? Did that work?

I also recommend trying this circuit on an evaluation board. This would help speed up the debug process.

9

Thanks for your constant support.

Yes, tried it multiple times. To no avail.

Yes, ordering the evaluation board is probably the logical next step.

10

Hi Felix,

Please send the Gerber files along with your project details to mpsnow@monolithicpower.com.

And keep us updated on the results through evaluation board testing.

11

Hi Felix,

I am closing the forum post here as we have emailed you from MPS Now.