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Recently I have been experimenting with the AP63203, and I just have not been able to get it to output 3.3V successfully. Currently, the way I have been testing it is using an SMT to TH adapter, which I have soldered the buck to and stuck it on a breadboard along with the \$4.7 \mu\text{H}\$ inductor and the other capacitors based on the diagram below: enter image description here

I have stuck with the recommended values as outlined in the datasheet, except for the inductor, as I don't have a \$3.9 \mu\text{H}\$ one.

With the first test, I supplied 24V to the input and noted that the power supply was shoring out. I tested the pins on the buck and realised that pins 4, 3 and 5 (GND, VIN and SW, respectively) are shorted together permanently, whether the buck had power or not. (See the image below for the breadboard layout, the top left of the IC is pin 1).

enter image description here

I repeated this with a brand new buck converter and, this time kept the input and output grounds separated, and I found that all 6 pins were now at about 24V (with respect to input ground), and the power supply was not shorting. I also found that GND (output) was not permanently shorted to SW this time around, so I am not quite sure what is going on. (See the image below for a slightly different layout where the grounds are separated).

enter image description here

I feel like I am making a very obvious mistake somewhere, but I can't see it, have I wired something incorrectly on my breadboard? If anyone could point me in the right direction, that would be greatly appreciated. TIA

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  • \$\begingroup\$ Did you get the correct IC (3V§ Fixed) or the adjustable Version? \$\endgroup\$
    – ElectronicsStudent
    Commented Dec 20, 2023 at 2:46
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    \$\begingroup\$ "and this time kept the input and output grounds seperated" - what does this mean? the IC only has one ground pin, and it's not going to produce an isolated output... \$\endgroup\$
    – Attie
    Commented Dec 20, 2023 at 2:54
  • \$\begingroup\$ The marking on the IC is T43SU, and paring that up with page 16 of the datasheet, I can confirm that it correlates to AP63203WU-7 - I am sure that it is the fixed variant. @ElectronicsStudent \$\endgroup\$
    – Лука
    Commented Dec 20, 2023 at 2:57
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    \$\begingroup\$ There is no way anyone can decipher from the breadboard photos how things are connected together. Even if there was a schematic it would be hard to prove from a photo that the breadboard circuit matches the schematics. \$\endgroup\$
    – Justme
    Commented Dec 20, 2023 at 6:28
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    \$\begingroup\$ Trying to breadboard this type of circuit is futile as you get stray inductances and connections with high resistance. The manufacturer specifies a pcb layout - this is not optional. \$\endgroup\$
    – Kartman
    Commented Dec 21, 2023 at 7:00

1 Answer 1

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I found the issue. Turns out the SMT to TH adapter I have been using didn't have long pins to make contact with the breadboard (Silly mistake, I know). Holding down the IC to ensure sufficient contact fixed the issue immediately, confirming that you can experiment with this type of circuit on a breadboard despite it being a SMD.

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