Comment on SMD Component Identification
jeinzi@discuss.tchncs.de 6 days ago
Feels an awful lot like a step-up converter. I’m missing the ground connection though and potentially a connection to a voltage divider for feedback. Where does R4 lead to? Are you sure there is no connection from the middle right pin except to C3? Is pin 1 of U1 marked? Can you make a detailled photo of the IC to better identify the text on it?
bruce965@lemmy.ml 6 days ago
Yeah these pictures are not the best, are they? 😬 I took some more, they might be a tiny bit clearer, but I’m afraid that’s the best I can do with my camera, link to pictures. Seems to be AL322 or maybe AL022? Neither of the two returns any results for me, though.
R4 leads to somewhere for sure, but it’s hidden below the IC, so I can’t follow it. To disasemble it any further I would need to break it entirely. I guess that’s an option. I checked the middle right pin again, it only seems to go to C3 as far as I can tell. Pin 1 of U1 doesn’t seem to be marked, at least not anymore, but perhaps it might be guessable from the direction of the text?
jeinzi@discuss.tchncs.de 5 days ago
I duckduckgoed “SOT23-6 boost converter” and found a picture of an IC with similar markings - I’m now pretty sure the component is an FP6291 switching regulator by Advanced Analog Electronics.
If you look at the datasheet, the “AL” identifies the part, and the following numbers are the year of production and the wafer lot number, so they could really be anything. The pinout matches as well, given a few inaccuracies in your schematic, which I think I can confirm on the images. Thanks for the image of the PCB against the light, that was very helpful. Pin 1 would be on the bottom right, connected to the inductor L1 to boost the voltage, with the other pins arranged counter-clockwise. Pin 2 should then be connected to your PCB ground; to confirm, you could use a multimeter in continuity mode to measure to the BAT- and 5- connections. The right side of R4 should also be connected to ground, and 24 kΩ would set the current limit of the IC to 2A (page 7). On pin three is one of the mistakes in your schematic as far as I can tell, I think that pin is really connected to the point between R6 and R5, for output voltage feedback. I also think R6 is meant to read “84D”, which would be the resistor code for 732 kΩ with 1% tolerance. If you calculate the output voltage of the regulator with the 0.6V feedback voltage from the datasheet and 732k/100k resistors, it comes out to 4.99V, which would be compatible with the USB 5+/5- stuff. Connecting EN to VCC (pin 4 to 5) is also common to permanently enable an IC, but I think there’s another error in your schematic: I’m pretty sure those two pins are directly connected to BAT+ instead of through C4, and that C4 instead connects from those two pins to ground to stabilize the input voltage.
bruce965@lemmy.ml 5 days ago
You must have spent a lot of time into this, thank you so very much 🙏
With a bit of persuasion I managed to disassemble it without breaking it. I desoldered U1 and I can confirm that pin 2 is GND. Also, here are better pictures taken with a magnifying glass. Note that pin 1 and 3 were shorted to pin 2, but it didn’t make sense to me, so I assumed they bridged due to the thermal shock when the component burned, so I scraped around them.
And here’s a link to AliExpress.
I guess there is no easy way to bypass it then, it would probably cheaper to buy a new device than to buy a replacement IC. Also, I guess now I will have to upload a clean version of the corrected schematic, I owe this to you and the other great people that replied.