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In this iPhone 6 schematic, why is the VCC line tied into the SW and VP pins? My confusion stems from thinking SW means switching as in a boost or buck circuit but because it's directly linked to VP which I'm guessing is the input for the ic it's throwing me off. I believe this link is the Datasheet for the ic https://www.cirrus.com/en/pubs/proDatasheet/CS35L01-03_F1.pdfschematic

And the entire circuit full

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  • \$\begingroup\$ (1) Can you find a datasheet for the CS35l19B-XWER and post a link? (2) Is this an iPhone schematic? (3) Can you rewrite your question to make it clearer to someone outside your head? I've read it five times and I still don't understand what you're asking. ;^) \$\endgroup\$ – Transistor Jul 29 '16 at 1:16
  • \$\begingroup\$ @transistor Lol edited original question answering your questions \$\endgroup\$ – ohmmy Jul 29 '16 at 1:23
  • \$\begingroup\$ That's better. That's the datasheet I found but the chip has nine pins. Your schematic has 42 (I think). What's going on? Cirrus don't list the CS35L19B-XWER. \$\endgroup\$ – Transistor Jul 29 '16 at 1:26
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In this iPhone 6 schematic, why is the VCC line tied into the SW and VP pins?

Notice that the incoming PP_BATT_VCC supply does not connect directly to the SW pins. Inductor L1604 is effectively between the SW and VP pins.

My confusion stems from thinking SW means switching as in a boost or buck circuit but because it's directly linked to VP which I'm guessing is the input for the ic it's throwing me off.

As I said, the SW pins are not directly connected to the VP pins :-) However there is some switching involved - see below.

I believe this link is the Datasheet for the ic https://www.cirrus.com/en/pubs/proDatasheet/CS35L01-03_F1.pdf

I don't think so. :-) That one is a much simpler audio IC. The specific IC in that schematic (CS35L19B-XWER) seems not to be generally available. However Cirrus Logic do sell another audio IC with similar power connections - the CS35L32 (datasheet).

That IC (in common with some other audio ICs) can operate at a lower voltage than the (higher) voltage used to drive the loudspeaker(s) (and, on the CS35L32, also used to drive the LEDs). Therefore the IC contains a built-in boost converter which can generate a higher voltage than its supply voltage. That requires an external inductor, and that is what L1604 is!

Look at the CS35L32 datasheet linked above and you will see it is a complex IC, but section 4 describes the power supplies, speaker amplifier and the boost converter which uses the SW pins. Looking at the external power connections and external inductor in the schematic extract you included, I believe that your questions about the CS35L19 SW and VP pins are answered by the relevant part of the CS35L32 datasheet.

Here is a diagram from the CS35L32 datasheet, showing the equivalent of the L1604 inductor (here marked LBST) between the SW and VP pins:

c35l32 built-in boost converter

So unless someone finds a CS32L19B datasheet, I hope that should be enough information to answer your questions.

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  • \$\begingroup\$ Good find but what's with the 42 pins on the iPhone schematic then? \$\endgroup\$ – Transistor Jul 29 '16 at 2:22
  • \$\begingroup\$ That diagram definitely helps the way vp is before sw. Apple made it look complex. I've added the entire schematic but it's screenshot from my phone so it'll be small and hard to see details. Maybe it'll help with the question about 42 pins \$\endgroup\$ – ohmmy Jul 29 '16 at 2:30
  • \$\begingroup\$ @transistor - Hi - "what's with the 42 pins " Thankfully, that wasn't the original question - if that had been the question, then I wouldn't have written this answer :-) The CS35L19B clearly has some different features than the CS35L32. As we know, ASIC manufacturers often re-use internal parts (blocks) where similar functionality is needed. I just applied that knowledge in this case, to see if the power supply functionality matched, and imho it is close enough. If someone wants to know the functionality of all pins, imho that would need the specific datasheet for the CS35L19. \$\endgroup\$ – SamGibson Jul 29 '16 at 2:34
  • \$\begingroup\$ @ohmmy - Hi - If you want to ask a new question requesting to know what all pins on that IC do, then I wish you good luck. But without finding the datasheet for that specific CS35L19B device, I doubt you will find such details easily. I was able to apply some reverse-engineering experience to this question about the power connections - but it is a different (and much bigger) question to do that for all the pins. If this is really important to you, then try to find the IC's datasheet. \$\endgroup\$ – SamGibson Jul 29 '16 at 2:37
  • \$\begingroup\$ @SamGibson Thank you your answer was sufficient, I merely edited to add the entire circuit as the user "transistor" asked about the other pins and thought it might help \$\endgroup\$ – ohmmy Jul 29 '16 at 2:40

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