MCP34063 in buck/boost topology

[bojankoce]

Hello, everyone.

I need to generate a stable 12V to supply my cooling fan (current consumption not over 200-300mA). The input voltage is in the range of 10V to 26V. Consequently, some buck/boost topology will be needed.

I came across the MCP34063 module. It is clear from the datasheet that it can work in the following topologies:

1. Step-up
2. Step-down
3. Voltage inverting

I wonder if there is a possibility to configure MCP3406 to work in both step-up and step-down modes and generate stable 12V at the output for the input voltages in a range from 10V to 26V?

Thank you very much guys for your time and efforts. Your help is really appreciated.

Looking forward to reading from you.

Sincerely,

Bojan.

[Peter BENSCH]

Yes, you can build a buck-boost regulator with the MC34063, but this requires both an additional power switch (classic pnp bipolar or possibly p-channel FET) and a second Schottky. However, it would have to be checked first whether this can work up to your desired 26V.

However, it is a fact that the MC34063 was developed almost 30 years ago and therefore still works with a very low switching frequency, which makes the passive components (L, C) quite large, bulky and expensive.

Would this effort be worthwhile for you?

Regards

/Peter

[bojankoce]

Hello, @Peter BENSCH​ .

Thanks for the prompt reply. I am generally interested in something small and simple that will generate me 12V at the output for the input voltages in a range from 10 to 26V.

Not happy to hear that MCP34063 requires bulky passive components.

Is there any better module (simple, cheap, with minimal external components) from ST that could help me achieve the goal? As I said, current consumption is not critical. It will not be more than 300mA @12V.

Cheers!

[Peter BENSCH · Accepted solution]

Well, 300mA at 12V doesn't sound like much, but 10...26V is a wide range to cover.

I did a quick calculation: Ipk would already be at the upper edge at 10V, even more at 26V, so the MC34063 is not suitable for this application.

Unfortunately, I can't recommend any other device from ST's portfolio with which you can easily set this up.

Good luck in finding the right device!

Regards

/Peter

[bojankoce]

Thanks for the clarifications, @Peter BENSCH​ ! Really appreciate your help.

Cheers! :clinking_beer_mugs:

[Peter BENSCH]

If the problem is resolved, please mark this topic as answered by selecting Select as best. This will help other users find that answer faster.

Good luck!

/Peter

[bojankoce]

The problem is not resolved for me but it is at least clear that MCP34063 is not an appropriate part. :grinning_face:

[Rompel]

Hi Mr. Bensch,

I was thinking to open a new case but also to ask my question under this case.

We are using the MC34063AB in our product since 20years and have update to MC34063EB due to some quality problem which still remain.

The product work well after some few time, but by making a temperature test, it fails and the error is "7V out of boundary"

After carrying out some measurement, the 7V is now 12V and changing the IC with a new does not help. Any idea?