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MC34063 - Current

Suraj143

Active Member
I need 12V to 5V converter with 600mA current. Going to use the attached circuit. will it be able to provide my required current?Does the chip gets heat?
 

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JimB

Super Moderator
Most Helpful Member
What does the datasheet for the MC3403 say?
Download it and have a look.

JimB
 

rjenkinsgb

Active Member
According to the datasheet, it is rated at 1.5A
https://www.onsemi.com/pub/Collateral/MC34063A-D.PDF

You should be well within its capabilities.

If you are considering using it in a mass produced design, build a prototype first to make sure it's OK in all environmental conditions it may be exposed to; eg. if it's in a sealed enclosure with other components generating heat, you need to see how the whole system works and parts interact.
 

MichaelaJoy

Active Member
like rjenkinsgb said. You have to prototype it and test it under load to know for sure.
 

dougy83

Well-Known Member
-deleted: completely incorrect-
 
Last edited:

ronsimpson

Well-Known Member
Most Helpful Member
This is going to the output current divided by the duty cycle, best case. So it looks like it's running at or above the upper limit.
From data sheet. (ST version)
Rsc 0.33 = 1A So the switch will open up at 1A and keep away from the 1.5A absolute limit.
I did not go through the math but the schematic in post #1 looks like the current will start at 400mA and turn off at 800mA in a typical cycle which will result in 600mA average. I don't see a prolbem. With the switch open the current in the diode will go from 800mA sloping back down to 400mA.
1551102212580.png
 

Suraj143

Active Member
Hi thanks for the help.

I built the circuit on a vero board.I placed a small coil inductor (220uH - 4X6 size) & also placed a 220uF on the output instead of a 470uF capacitor.All other parts remains as in my first post schematic.

Results
=======
The coil gets really hot within the first two seconds.Really hot & comes with a bad smell.I turned it off immediately.I guess that the inductor is not enough.Going to add a high current inductor.I will tell the progress.
 

Suraj143

Active Member
Good news guys.
I replaced the inductor with a bigger one, 220uH Results good.Did a load test by loading a 600mA continuous current.The IC is getting some heat. Is it normal? Here is the schematic of my values.
Is there any method to lower down the heat in IC...!!!
 

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