MC34167 Stepdown converter

[skylerdprahl]

https://www.onsemi.com/pub_link/Collateral/MC34167-D.PDF


Look at figure 19 for me. I designed it properly, laid it out good. Everything works good LOL

How do I control the output current? or is that not possible with this chip?

Voltage is 5.03 without a pulldown resistor at R1. I can adjust the voltage with different values of R1 but how am i to adjust current output?

I would like it limited to around 4@, I have voltage adjusted to 11.5v with a 12.2v-13.8v power supply.

 

[FoxyRick]

The MC34167 has no means to adjust its current limit; it is internally set/fixed.

 

[skylerdprahl]

shite... Is there anything simple like this that has a way to set current?

I thought the inductor had something to do with the current?

blah... What does the inductor do?

 

[mtwieg]

The MC34167 doesn't regulate output current in the first place. It just regulates peak input current, which is only roughly related to the average output current. Getting an accurate limit on average output current generally requires a separate feedback loop, which simple controllers won't have. If you are fine with just regulating peak current, then you can get other controllers with external sense resistors, allowing you to choose the limit.

 

[FoxyRick]

The inductor is an energy storage component; nothing to do with current limiting.

The LM2679 has adjustable current limiting by way of an external resistor. Perhaps that would suit your purpose. It has several versions, the adjustable part number is LM2679SD-ADJ.

https://www.ti.com/product/lm2679

https://www.ti.com/lit/ds/symlink/lm2679.pdf