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problems with MIC4830

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uhu1313

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I have built the typical applicaiton circuit from teh MIC4830 datasheet. I have used the values for 0.4inch2 EL panel running at 900Hz (REL=0.369MOhm, RSW=321kOhm). The input voltage is 3.3V My problem is that the output voltage is around 40Vpeak-to-peak. I have checked all pins with an oscilloscope, the waveforms seem to be OK, switching frequencies are very close to the required values. I don't seem to find what could be wrong. Any ideas why am I getting a too low output voltage?

Thanks.
 

Hi,

Pictures say more than a lot of words.
Please post a link to the datasheet.
the output voltage is around 40Vpeak-to-peak.
And what do you expect?

Did you use the recommended PCB layout?
Did you use exactly the recommended parts, especially inductor and capacitors?

Klaus
 

Hi,

Pictures say more than a lot of words.
Please post a link to the datasheet.

And what do you expect?

Did you use the recommended PCB layout?
Did you use exactly the recommended parts, especially inductor and capacitors?

Klaus

Hi, the datasheet is here:
https://ww1.microchip.com/downloads/en/DeviceDoc/mic4830.pdf

I have used the exact recommended parts, the pcb is the one in the evaluation board (https://ww1.microchip.com/downloads/en/DeviceDoc/MIC4830YMM Evaluation Board User Guide.pdf) modified to be a bit smaller (removed the unnecessary texts, etc.)
The inductor is exactly the recommended part (LQH4C221K04), the output capacitor is 2.7nF 250V dielectric, the switching diode is the exact same part (BAV20W)

I was expecting an output voltage of around at least 150Vpp.
 

Can your 3v3 source supply enough power ...?

- - - Updated - - -

At 900Hz you'll need a larger storage cap on the boost ..

- - - Updated - - -

Your EL may be faulty or way over sized ...
 

Is your panel sizes 0.4inch2 ?
I checked your values OK!
CS Voltage should be around 76-99 V
 
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Hi,

Show a couple of detailed photos.

Klaus
 

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