Can someone explain this circuit to me?

[caphair]

This is the backlight circuit for an iPhone 6

I'm confused at the line out (D1) because the ic says OVP doesn't this mean over voltage protection?

Then below it D3 and D2 (LED1, LED2) wouldn't these be the lines out for the backlight or are these for limiting the brightness?

[gabiz_ro]

Re: Can someone explain this circuit to me?

D1 is not output
Is indeed OVP.
Like other IC,OVP function could be tied to output or to some divider circuit from output.
Pulses are rectified by D1501.
In case you don't need OVP then don't connect,but I don't have datashhet for this IC to check what conditions are required on OVP pin.

D2 and D3 are ILED and are some kind of adjustable constant current.

IC boost voltage from battery.OVP prevent over voltage.Current flow from diode cathode through some number of LED's,one string,to ILED1 or 2 here current is controlled via software to obtain variable backlight level.

Hope my english was good enough so you can understand what I write.

[caphair]

Re: Can someone explain this circuit to me?

Thank you. From the schematic D1 goes to the backlight connector of the screen.

So you're saying even though it is OVP it can still be the output that drives the backlights?

[gabiz_ro]

Re: Can someone explain this circuit to me?

No.
Real output is on cathode of diode D1501.

OVP is tied to this to monitor output voltage.
OVP is input for IC.

Since is same track from cathode to cap's and to OVP,is same track,or traceline,to backlight connector.

[caphair]

Re: Can someone explain this circuit to me?

No.
Real output is on cathode of diode D1501.

OVP is tied to this to monitor output voltage.
OVP is input for IC.

Since is same track from cathode to cap's and to OVP,is same track,or traceline,to backlight connector.

Ah ok. Makes sense now. Thanks. Do you know the purpose of the other pins? (Lower half of the ic)

[gabiz_ro]

Re: Can someone explain this circuit to me?

A1,A2 are SCL and SDA.
I2C bus line to main CPU.

C1 is VIO SPI. 1.8V power for IO SPI and maybe I2C

B1 is backlight enable.But seems to be enabled by Vcc of SDRAM,so always enabled if powered iphone,0 value or off state may be controlled by software.

B2 and C2 are second bus line,SPI ones.
Seems connected to CPU-PMU (proccesor-power management unit)

Without datasheet don't know why is used both I2C and SPI bus lines.

[retiredcaps]

Re: Can someone explain this circuit to me?

Have no idea since I have no interest in iphones, but saw this youtube video just posted

iPhone 6 backlight problems---how to rebuild the backlight circuit and why you have to

https://www.youtube.com/watch?v=8I9MlOkpR3k

[budm]

Re: Can someone explain this circuit to me?

Read the spec sheet to see the pins function, similar to LM3533.
LED backlights controller with Boost Converter (L1503, D1501, IC) and constant current controller to maintain constant current through the LEDs.

[caphair]

Re: Can someone explain this circuit to me?

Have no idea since I have no interest in iphones, but saw this youtube video just posted

iPhone 6 backlight problems---how to rebuild the backlight circuit and why you have to

https://www.youtube.com/watch?v=8I9MlOkpR3k

Wow did you read the comments with the member "mrsemifixit"? I have to agree with what he's saying. She doesn't seem to know much about how a circuit could fail in some instances. She does that for a living? Pretty surprising

[caphair]

Re: Can someone explain this circuit to me?

Read the spec sheet to see the pins function, similar to LM3533.

Thanks! I couldn't find the spec sheet when I searched?

[retiredcaps]

Re: Can someone explain this circuit to me?

Wow did you read the comments with the member "mrsemifixit"?

I, as a rule, never read youtube comments. I hate the columnar reading format. I also found in the past, people don't use any resemblance of English, grammar, punctuation, etc. Thus, I don't bother.

I have watched a few of her videos and she is one smart woman so unless I read the comments, I will give her the benefit of the doubt.

There are people who list themselves, voluntarily, as professionals here on the forum that post very dubious advice and show they lack fundamental skills. I could point out a few threads, but I'm not that type of person and I have better things to do with my time.

[caphair]

Re: Can someone explain this circuit to me?

I agree but I thought it was an interesting exchange as she kept defending her claim that diodes don't fail shorted. Here's the last two comments