Cypress Type-C Barrel Connector Replacement + Infineon Buck DC/DC (Part 2)

Summary

In this article I will show you how to use a Keithley 2380 (actually two different ones) to test the output of the IRDC3894 12V->1.2V 12A buck development kit.

The Story

To this point I have written several articles about my process of designing a power supply for my new IoT device.  It needs to provide for quite a bit of power, actually 60W is what I am planning on.  I really wanted to make sure that the IR3894 chip would do what it says it would, specifically supply 12A.  The development kit is pretty simple.  There are two banana plug to  provide power to Vin and two banana plus for the load.

For this round of tests I will Keithley 2230-30-1 to provide power and I will use my Keithley 2380-120-60 to serve as the load.

The two mini grabbers are attached to to remote sensing terminals on the Keithley 2380.

After I had it all hooked up I went in 1A increments from 0 to 12A, then I went in 0.1A increments until I ran out of input power.

Here is the actual data table.  Note that I added columns to show the calculated input power.  And I calculated the efficiency of the system Wout/Win

Vin Iin Win Vout Iout W Eff
12 0.27 3.24 1.198 0 0 0%
12 0.129 1.548 1.198 0.998 1.195604 77%
12 0.239 2.868 1.198 1.998 2.393604 83%
12 0.345 4.14 1.198 2.998 3.591604 87%
12 0.454 5.448 1.198 3.998 4.789604 88%
12 0.564 6.768 1.198 4.999 5.988802 88%
12 0.677 8.124 1.198 5.998 7.185604 88%
12 0.792 9.504 1.198 6.998 8.383604 88%
12 0.909 10.908 1.198 7.998 9.581604 88%
12 1.029 12.348 1.198 8.998 10.779604 87%
12 1.152 13.824 1.198 9.999 11.978802 87%
12 1.277 15.324 1.198 10.998 13.175604 86%
12 1.406 16.872 1.198 11.997 14.372406 85%
12 1.42 17.04 1.198 12.098 14.493404 85%
12 1.434 17.208 1.198 12.198 14.613204 85%
12 1.448 17.376 1.198 12.297 14.731806 85%
12 1.462 17.544 1.198 12.398 14.852804 85%
12 1.477 17.724 1.198 12.498 14.972604 84%
12 1.49 17.88 1.198 12.59 15.08282 84%

When I plot the data there is something sticking out like a sore thumb.  WTF?  At first I assume that I typed in the wrong number when I transposed the hand written data to the spreadsheet.  So I went and looked at the data table where it appears that I typed it in correctly.  Does the efficiency really have a peak like that?

I decided to go remeasure the 5A datapoint.

Then I looked at my handwritten data sheet where I find that I transposed the last two digits of the input current. (I definitely should automate this measurement)

OK… now the plot looks way better

When I compare the plot from the data sheet versus my data on the same scale (about) they look very similar.  All seems good.