MC33063A-Q1: 12V 5V regulator chip getting too hot

Hi Salil

what is the loading when the case temperature is 60 deg?

what inductor part number?

Hi Jasper,

The load when the case temperature is 60 deg C is 360mA,

The Inductor part number is SRU1048-221Y

Thanks

Salil

Hi Salil,

the inductor saturation current is smaller than the current limit 1A. could you try to select a 1.5A level saturation current inductor?

Hi Jasper,

Increasing the Inductor size would be a significant cost increase. We are actually looking to scale down the Inductor size because it is already too big.

The 360 mA I mentioned earlier is actually the maximum load that the chip will ever see. This was the same constant load at which the chip case temperature climbed to 60 C in a matter of seconds and eventually reaches 80 C. 

Can changing the short circuit resistance value to 0.6 Ohms instead (limit current to 500 mA) be a better option?

Separate from this I did another test by loading the chip to 1A and the case temperature reached 125 C (Inductor never had any significant heat buildup).

Thanks

Salil

Hi Salil,

as the device typically operates at PFM, setting the current to 600mA would limit the output current capacitor to 300mA level.

the first step is find the root cause, if the inductor saturation is the reason leading to high temperature. it is not the solution. 

the performance of MC is actually not good, considering it is very old device.

why did you select this device, not a fully integrated buck converter, solution cost of which may be lower.

Hi Jasper,

I understood what you are saying, and I do have a 100uH inductor that has a saturation current of 1A (SRU1048-101Y).

Do you think that can work? 

As far as the decision to use this part is concerned, a lot of the buck converters that came up in my search were based on 33063 and 34063 parts this allows for many substitutes. I chose this MC33063 because it has ESD protection and can run to a junction temp of 125C. Other buck converter chips with the same capability were actually more expensive.

I am currently evaluating a different buck converter circuit for a new revision of my board, but I am still trying to find a solution for the older versions that have the MC33063 chip.

Having said that I am also open to suggestion on other buck converter chips if you want to recommend some?

Requirements are:

1) Chip should be able to withstand more than 40V on the Input side

2) Adjustable voltage output

3) Can carry a max load of up to 1A on the output such that chip case temperature does not reach more than 40C above ambient at full load.

Thanks

Salil

Hi Salil,

the 100uH inductor may work. the MC device can't support 1A output current. I change the post the wide VIN buck forum.