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Electronics => Repair => Topic started by: Hauke on January 01, 2019, 07:37:46 pm

Title: Need help identifying DC/DC converter
Post by: Hauke on January 01, 2019, 07:37:46 pm
Hi folks,



I've a circuit where I strongly suspect that a voltage regulator is broken. It converts 5V DC to 1.2V DC, needing to drive a few mA max. It is labeled "G82AA" and is a SOT23-5 package. I sketched the surrounding circuitry (and made assumptions on the pins):

(https://projects.webvoss.de/Downloads/U4-Circuit.jpg)

It looks somewhat similar to e.g. the adjustable Step-Down converter LM3670 (see page one of the datasheet (http://www.ti.com/lit/ds/symlink/lm3670.pdf), image "Typical Application: Adjustable Output Voltage"), however with a different pinout, which seems to follow Microchip (http://ww1.microchip.com/downloads/en/DeviceDoc/22042B.pdf), STmicroelectronics (https://www.st.com/content/ccc/resource/technical/document/datasheet/22/99/6c/42/0d/cc/47/8f/CD00181873.pdf/files/CD00181873.pdf/jcr:content/translations/en.CD00181873.pdf) or Richtek (https://www.richtek.com/assets/product_file/RT8059/DS8059-06.pdf) devices (and some others).

Googling and looking at a few shops like Mouser or digikey I could find nothing matching, but the choice to pick from is *huge*!

Can anyone give me helpful hints how to find a matching replacement part from the hundreds of available DC/DC converters?

Thanks!

Hauke
Title: Re: Need help identifying DC/DC converter
Post by: fzabkar on January 01, 2019, 08:05:52 pm
The 1:1 potential divider would suggest that the feedback voltage is 0.6V. Therefore I would be looking for a regulator that is rated for a minimum output of 0.6V.

You might also try creating a BOM for the circuit. Sometimes a designer will favour one particular IC manufacturer, so if you can identify the other ICs, then this may help you to identify your regulator.

Edit:

TS3406, Taiwan Semiconductor, 600mA / 1.5MHz Synchronous Buck Converter, marking G8ywx, SOT-25, Vin = 2.5V - 5.5V:
http://www.mouser.com/ds/2/395/TS3406_C12-249000-1206809.pdf (http://www.mouser.com/ds/2/395/TS3406_C12-249000-1206809.pdf)
Title: Re: Need help identifying DC/DC converter
Post by: Hauke on January 01, 2019, 09:38:28 pm
Hi fzabkar,

thanks for the hints! Thats very helpful, narrows down the search!

Regarding BOM: Very mixed vendor set on the PCB... No luck here, still: very good idea.

Cheers

Hauke
Title: Re: Need help identifying DC/DC converter
Post by: Armadillo on January 01, 2019, 09:39:33 pm
The output voltage is 1.2v from the 1:1 divider, not 0.6V.
Title: Re: Need help identifying DC/DC converter
Post by: fzabkar on January 01, 2019, 10:37:05 pm
The output voltage is 1.2v from the 1:1 divider, not 0.6V.
The voltage at the feedback pin is 0.6V. That's the divider's output AISI.
Title: Re: Need help identifying DC/DC converter
Post by: Hauke on January 12, 2019, 06:20:39 pm
Hi fzabkar,

I'd like to thank you again for your help! Looking more closely on your suggested part it turned out to be exactly the one I needed. I was able to get a compatible part from my local electronics shop, and even better, it was indeed the faulty part of the circuit and the thing is repaired! So praise to fzabkar!

Can you tell me how you were able to find that part? Is there some search engine that allows to look for housing markings? If so, I'd be happy to learn about it, since I spent hours searching for the part myself with no success.

/me is happy!

Cheers

Hauke
Title: Re: Need help identifying DC/DC converter
Post by: fzabkar on January 12, 2019, 07:43:41 pm
I used these search terms:

https://www.google.com/search?q=filetype:pdf+converter+marking+g8 (https://www.google.com/search?q=filetype:pdf+converter+marking+g8)
Title: Re: Need help identifying DC/DC converter
Post by: shakalnokturn on January 13, 2019, 01:47:26 am
One member (I can't remember who) posted his trick a few months back, and it was great advice, I found plenty of unknown SMD references thanks to that:

Search with marking code and package on the Chinese TAOBAO website.

Unfortunately the website now appears to require registration before searching.