Help identifying an SMD - Page 1
Forum section: electronics / repair

author: astrojucar
author_rank: Newbie
timestamp: August 05, 2021, 09:31:51 am
content: It is part of an HDMI over Cat-6 receiver. It is shorted and gets REALLY hot.I haven't been able to find anything on google.I am lost, do any of you know by any chance what that is and how to replace it?Thanks!

author: phlegeton
author_rank: Contributor
timestamp: August 05, 2021, 10:45:40 am
content: The only reference I could find in a SMD codebok (http://caxapa.ru/thumbs/588912/smd-codes.pdf) is:SMDcode Type Function Short description Case Pin. Mnf.ABDO MAX6306UK31D3-T CMOS-IC Voltage Detector 3,1V, -MR, -Reset ODO, 140ms SOT-23-5 28ek - Max(Of course not sure if this is the right part. )

author: astrojucar
author_rank: Newbie
timestamp: August 05, 2021, 10:46:55 am
content: Thanks! I think it is a 1.2V regulator because the main chip uses that voltage.

author: fzabkar
author_rank: Super Contributor
timestamp: August 05, 2021, 10:15:27 pm
content: It appears to be an adjustable step-down converter.1 = Vcc2 = Gnd3 = Lx4 = N/C ?5 = FBIf you can measure the two resistors at the FB pin (R8 & R9), then we will be able to work out the FB voltage. That will then help us to search for suitable replacements.Have you measured the resistance between the coil and ground? That will tell us if the load is shorted rather than the IC itself.What are the markings on U1? Perhaps it is manufactured by the same company?

author: gamalot
author_rank: Super Contributor
timestamp: August 05, 2021, 11:03:42 pm
content: Could be SY8008Bhttp://www.sunnyqi.com/upLoad/product/month_1306/SY8008.pdf

author: mariush
author_rank: Super Contributor
timestamp: August 05, 2021, 11:05:10 pm
content: Definitely a switching regulator.I'd check those 3 ceramic capacitors on the input, make sure they're not shorted . The smallest looks much darker than the others, which could be a sign of being shorted, but could also be just a different composition. Do the same on the output, it's easy to check.Yeah, resistors will tell you the output voltage. Most likely the chip has a 0.6v voltage reference, or maybe 0.8v... less likely it will be a more generic 1.25v reference voltageI don't know the formula off the top of my head...it's something like reference voltage x ( 1 + R1/R2) or something like that. You can pick any high frequency synchronous rectifier switching regulator off digikey or mouser or whatever and look in datasheet for the formula.It's not that SY8008 chip, because there doesn't seem to be an ENABLE pin and the inductor is obviously connected to other pin, not like in the pdf.

author: fzabkar
author_rank: Super Contributor
timestamp: August 05, 2021, 11:56:28 pm
content: Quote from: gamalot on August 05, 2021, 11:03:42 pmThat would be a possibility only if pins 1 and 4 were connected underneath the package.

author: amyk
author_rank: Super Contributor
timestamp: August 06, 2021, 03:00:25 am
content: Pretty sure it's SY8008BAAC. 1 and 4 are almost certainly connected underneath, and there may be a via or two under there too.

author: gamalot
author_rank: Super Contributor
timestamp: August 06, 2021, 08:23:41 am
content: I didn’t say that it must be SY8008B because the inductor L2 is 2.2uH and in some schematics I found it is 4.7uH. Later I realized that SY8008 and RT8008 are pin-to-pin compatible, and a 2.2uH inductor used in typical application of RT8008.

author: amyk
author_rank: Super Contributor
timestamp: August 07, 2021, 03:24:26 am
content: RT8008 has different marking. Marking of OP's part matches SY8008BAAC.As for the inductor, the datasheet for the SY8008 characterises it with a 2.2u inductor.

author: gamalot
author_rank: Super Contributor
timestamp: August 07, 2021, 10:31:53 am
content: Quote from: amyk on August 07, 2021, 03:24:26 amI know they have different markings, I'm just saying that they are pin-to-pin compatible, so they should have the same peripheral components.Components in the schematics in the datasheet of SY8008 have no values. After reading your post, I found that the inductor's value is mentioned in the electrical characteristics table.

author: TurboTom
author_rank: Super Contributor
timestamp: August 07, 2021, 10:39:25 am
content: Shanghai Belling BL3406B-1.2VBut the aforementioned Sy8008 will fit the bill as well.