SMD Component Identification

Submitted ⁨⁨6⁩ ⁨days⁩ ago⁩ by ⁨bruce965@lemmy.ml⁩ to ⁨askelectronics@discuss.tchncs.de⁩

https://lemmy.ml/pictrs/image/5366dbbe-bceb-4393-bb6e-3b3488ce3da9.png

Hi! I recently purchased a nice gadget from AliExpress, this should be the circuit to drive an ultrasonic piezo. Silly me, I put the batteries backwards and the U1 component on the bottom left blew up.

I know a bit about circuits so I reverse engineered it (there might be mistakes), but I am not skilled enough to identify the component in order to look for a replacement. Can someone help me identify it? I can read ___22 on it.

Here’s another version of the schematic, which might be easier to understand.

Schematic

Thank you for your help!

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partial_accumen@lemmy.world ⁨6⁩ ⁨days⁩ ago
The photo isn’t great, but it looks like a 6-pin package. From your schematic I would assume its part of the battery charging circuit.

You say it “blew” is it shorted or open? If open, then my guess is the rest of the device should function, you just won’t be able to charge the battery. If its shorted, I could see that draining any current away from your piezo driver.

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- bruce965@lemmy.ml ⁨6⁩ ⁨days⁩ ago
  Sorry about the pictures, that’s the best I could do with my phone camera. I took some more, they are not much clearer, but there are more angles at least, link to pictures. It certainly is a 6-pin package.
  
  It didn’t occur to me that it could be part of the battery charging circuit, that would be nice. I am a bit worried about plugging batteries again, as I am afraid I might damage it further. Assuming pins on the left to be 1, 2, 3 from the top and pins on the right to be 4, 5, 6 from the bottom: pin 1, 2, 5 and 6 seem to be shorted, pins 3 and 4 give me 90k resistance.
  
  I didn’t try image search, do you mean on Google Image Search?
  
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  - partial_accumen@lemmy.world ⁨6⁩ ⁨days⁩ ago
    
    It didn’t occur to me that it could be part of the battery charging circuit, that would be nice as honestly I don’t care about using it as a battery charger (it takes two AA).
    
    I’m a bit confused. Two AA batteries usually means 3v DC which is common to power a device. However, in your schematic on the left hand side, you have a symbol that represents a battery, its labeled 5v, and USB. I assumed this was the power source for the device. If not, why does your device have two power sources and one is not rechargeable.
    
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  - jeinzi@discuss.tchncs.de ⁨5⁩ ⁨days⁩ ago
    There’s no way U1 is charging the battery. How would it? If the connection labeled USB is the power source, it’s only connection to U1 is through a 100k resistor and a reverse biased diode. Also, charging AA batteries? Sure, you could plug in some NiMH cells, but then the device would need to have explicit instructions telling you that this is indeed a charger and to only ever insert rechargable AA battery cells.
    
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ThePantser@sh.itjust.works ⁨6⁩ ⁨days⁩ ago
Sounds like a job for Big Clive. Although idk how to contact him. Maybe you would need to join his Paterion.

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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?

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- 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?
  
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  - 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.
    
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Noodles4dinner@hexbear.net ⁨6⁩ ⁨days⁩ ago
[deleted]
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- bruce965@lemmy.ml ⁨6⁩ ⁨days⁩ ago
  I don’t get it 😅
  
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