mc34063a ic heating up

shyam kumar

Other Parts Discussed in Thread: MC34063A

Hi,

I am using mc34063a ic as 12v to 3.3v regulator at 400mA load current. The problem is, IC is getting heated up a while after powering up.

Can u please suggest a solution?

attached is the design we are using. Inductor selected is 150uh having saturation current of 530mA.

sense resistor we are using two 0.68 ohms in parallel.

can you please review the schematics and let me know the reason?

over 9 years ago

0 Ron Michallick over 9 years ago

TI__Guru**** 152566 points

Shyam,

Peak inductor current could be as high as 0.3V/(.68ohm/2) = 900mA.
This is beyond the inductor saturation current.

Measure pin 2 waveform with an oscilloscope to see switching signal.

0 shyam kumar over 9 years ago in reply to Ron Michallick

Prodigy 20 points

we changed the inductor which has the value 120uH, 890mA. But still the MC34063A is heating.

Please suggest a suitable solution.

0 Ron Michallick over 9 years ago in reply to shyam kumar

TI__Guru**** 152566 points

Shyam,

Have you looked at pin2 waveform?
How hot is the MC34063A?
If no measurement, too hot to touch lightly or firmly?
I see nothing wrong.

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mc34063a ic heating up