Diodes Inc AP62300

[hpmaxim]

Has anyone used Diodes AP62300 (or 62200, 63300, etc)?  It's a cheap/simple buck converter with internal switch.  I designed a board based on Figure 1 of their datasheet.  Albeit my component values differed a bit.  My values were as follows:

C1 22uF (this was actually part of a Pi filter, so there were 2 22uF caps with a 10uH inductor in between).
C3 1uF
R1 52.3k (with 47pF in parallel)
R2 10k
L 10uH
C2 2x22uF with a diode between them.  There is also a 1000uF electrolytic in parallel with the 22uF on the cathode side of the diode.

When I power the circuit up, it starts drawing current as if its a resistive short between power and ground.  I have four different boards, they all do the same thing although the resistance varies from about 5 to 20 ohms.  Hitting it with a thermal camera shows the part as the only heat source on the board when I power up the input.

I don't think it's powering up the output.  Nothing on the board seems active.  The diode I mentioned on C2 has another parallel diode, effectively an alternate way to power the board up without going through the AP62300.  When I power that side up, it draws about 90 mA @ 5V which is about what I'd expect.  There is some inrush given that electrolytic, and my Riden 6006 power supply acts a bit goofy if I don't turn the current limit up a bit beyond the 90mA, but 150mA is adequate for it to start up correctly.

I've tried contacting Diodes Inc, but they are not being responsive.

https://www.diodes.com/assets/Datasheets/AP62300_AP62301_AP62300T.pdf

[sd]

Have you connected EN to VIN directly? If so, is VIN higher than 6V?

[hpmaxim]

Yes, EN is directly connected to VIN.  I was nominally trying to power it with 12V, but I did try lowering the voltage, down to see if there was a relationship between I and V since I was hitting compliance on the power supply (trying not to blow up the parts).

[georges80]

EN has a max input rating of 6V. You are NOT meant to connect it to VIN. If you want it to start up on its own, leave EN *NOT* connected. Read the data sheet.

I've used various parts in that family, just working on an AP62200 based design. Chip works properly, EN *NOT* connected.

cheers,
george.

[hpmaxim]

Welp, looking at the datasheet it does appear to say abs max voltage on EN is indeed 6V.  Looking at the layout, not only are VIN and EN shorted, but it's shorted in a trace that goes under the part, so either I have to pull the part and cut it with an x-acto, or possibly cut the pin off the package and then try to de-solder it from the pad.

What are the chances that I didn't blow up the part?  Can you confirm excess current draw and failure to turn on if EN is too high?

[georges80]

^ replace the part, it has a 6V spec and you blasted it with 12V. Given it is misbehaving, it's a decent assumption that damage has been done.

Like I wrote, I've used various parts in that family (decent low quiescent current) and I've never had issues getting them to work reliably and long term. I've used 1000's of the parts in various production designs.

I'd also check your layout, I assume you've followed appropriate DC:DC converter rules with copper flooding, FB pin stuff not routed around/near the inductor path etc etc.

cheers,
george.

[hpmaxim]

Good call...

I pulled the old part, cut the trace and then soldered in a new one, and it powered up pulling 40mA@12V, which seems like a ridiculously reasonable number considering I was pulling about 90mA@5V.

[deanclaxton]

I'm using this part on a design and have some issues with setting the UVLO (Under Voltage Lock Out) resistor values. The datasheet gives a couple of formulas which I've input into a spreadsheet. I was aiming for VOn  = 11.5V, VOff =11V. Plugging that in I came to a preferred value for R3 of 81k6, and R4 of 8k56.

Now in practice, Voff is about right, but Von is more like 12.2V which is pretty much what it should be given the EN pin has a 1.2V threshold and the divider mentioned gives EN = 0.099Vin.

Anyone else used this part and set up the UVLO via resistor divider? The formulas seem a bit off in the datasheet.

[Miti]

Very interesting! I’m using AP63203 in one of my projects and I connected the EN input to the 12V input voltage. My heart stopped for a moment but after checking the data sheet, the EN input for AP63200 family is rated at 35V and for AP6200 family at 6V. If you look at the block diagram they look very similar. Hmmm, I wonder if there’s a mistake in the specs. But which one is wrong? My boards seem to be happy with 12V at the EN input.

[thm_w]

Very interesting! I’m using AP63203 in one of my projects and I connected the EN input to the 12V input voltage. My heart stopped for a moment but after checking the data sheet, the EN input for AP63200 family is rated at 35V and for AP6200 family at 6V. If you look at the block diagram they look very similar. Hmmm, I wonder if there’s a mistake in the specs. But which one is wrong? My boards seem to be happy with 12V at the EN input.

Basically zero chance the spec is wrong.
But yeah with the 20k series resistance, you wouldn't think 12V would cause any problems. Maybe some ESD additional elements are not shown?