Identify ICs on Huawei Mateview 28.2 4K monitor motherboard

[Timp74]

Hi All, Could anyone help with identifiing the following 2 ICs? The first I think it's a bucks/boost converter with integrate mosfets. Marking in BORDEC(or BQRDEC) It's a modified QFN package. Not sure what the second is, marking ADEAJ 8 pin. Possibly logic gates of some sort...

Thanks.

[tom66]

For a buck converter like this, if the converter is working correctly you will measure a DC voltage equal to the reference voltage across the bottom feedback resistor, i.e. the one that has one terminal grounded. The Vref for this part is 0.6V. If you measure the actual resistor values you can calculate the output according to the equation in the datasheet, but if you measure 0.6V across that lower resistor you can be almost certain the converter is working correctly.



Rearranging the equation for Vout is elementary algebra:

R2 = (0.6/(Vout-0.6))R1
R2(Vout-0.6) = 0.6R1
Vout-0.6 = (0.6R1)/R2
Vout=((0.6R1)/R2)+0.6

This is often factored as Vout=0.6(1+(R1/R2)) for another SMPS IC with a different Vref replace 0.6V as appropriate.

[Timp74]

I think the first IC is BQRxxx, a Silergy SY21618 Single Inductor Synchronous Step Up/Down Regulator. Which doesn't seem to be available anywhere :/

[Timp74]

The second smaller IC is something like the SY21154, a step down regulator. It would be great if someone could tell me the values of R1 and R2 (circled) or what output voltage this should be giving. Seems to supply power to the WiFI option card via a dual load switch to the left of the first IC mentioned above.

[tom66]

For a buck converter like this, if the converter is working correctly you will measure a DC voltage equal to the reference voltage across the bottom feedback resistor, i.e. the one that has one terminal grounded. The Vref for this part is 0.6V. If you measure the actual resistor values you can calculate the output according to the equation in the datasheet, but if you measure 0.6V across that lower resistor you can be almost certain the converter is working correctly.



Rearranging the equation for Vout is elementary algebra:

R2 = (0.6/(Vout-0.6))R1
R2(Vout-0.6) = 0.6R1
Vout-0.6 = (0.6R1)/R2
Vout=((0.6R1)/R2)+0.6

This is often factored as Vout=0.6(1+(R1/R2)) for another SMPS IC with a different Vref replace 0.6V as appropriate.

[Timp74]

Thanks Tom66. After working out the ICs the SY21154 powers I took a guess at it being 5v. I used the formular you provided to get the right resister values. I had to replace two other bucks converters(JW5213/JWG1J) that were powered off the 5v line to give 1.1v and 2v lines. The display seems to be working again now. Honestly I'm supprised I didn't have to replace any of the bigger ICs.

[tom66]

Nice to hear, glad you got it working.

[Timp74]

Seems I wrote too soon. The EEPROM that holds the HDMI EDID has been damaged, so the HDMI port no longer works properly. The EEPROM is powered via a diode from the 5v/SY21154 rail. The HDMI port still works with a macbook at 1080p, but windows and linux don't detect the display. Would be great if someone could share the HDMI EDID from their Mateview 28" monitor...