[SOLVED] IPhone wont charge with DC/DC converter

[Hawaslsh]

Hello,

I have a DC/DC converter that was designed using Ti's wbench. The circuit uses the LMR33640. I posted the schematic below, and I followed the layout suggested by Ti and the wbench software. The converter seems to work as expected. I supply and input of 12V, and using an electronic load I can draw the desired 2-3 amps. There are test points for ground and +5 next to the regulator for an oscilloscope. Under load, the output doesn't look too bad, maybe 30-35mV p-p around 5V.

When i plug in almost all USB devices they begin to charge. Power packs, amazon fire, all cheapo Chinese kids' toys. However, not my Iphone! It's an old Iphone S. The phone will charge in all other instances: wall plugs, computer's USB plug... etc. Is there something special about charging Iphones I am not aware of? Or is my regulator too noisy?

Happy to provide much more context, just wanted to ensure I am not missing something apple specific before going into more details.
Thanks in adance,
Sami

 

[betwixt]

I have no experience with charging iPhones but my guess is they use one of the USB data lines to set the charging rate and you do not have it connected.
Not a PSU problem but a socket wiring one.

Brian.

 

[cupoftea]

Get a USB connector with cables attached to it....cut it up, and splay out all the wires, and see what comes out of a "Normal" USB charger......you will see some of them have signals which the iphone expects to read.

Otherwise, yes, it could be a noise issue, and a good old common mode choke at the output of your converter could be a good idea...and a decent ceramic capacitor at its output.

In the mysterious world of chargers, there is a concept called "power delivery", and this sets all the usb charging parameters......those "Other" signals that you get in usb connectors.

 

[D.A.(Tony)Stewart]

Apple has always used some R or voltage termination scheme to identify approve sources. It may have migrated to data communication at some generation level.

GPT says this. Trust but verify!

Apple has indeed employed various methods to authenticate and identify approved accessories and sources over the years, particularly in their charging and data transfer cables. Initially, the company relied on resistance-based schemes, like the 30-pin dock connector and later the Lightning connector, which utilized specific resistor values to confirm the authenticity of connected devices.


As technology evolved, Apple shifted towards more sophisticated authentication methods, particularly with the introduction of the Lightning connector. This includes digital communication protocols that allow devices to exchange information, ensuring that only authorized accessories can communicate with Apple devices. This approach enhances security and enables features like fast charging and additional functionalities in accessories.


With USB-C adoption, Apple has continued to use similar principles, incorporating digital authentication and communication to ensure compatibility and performance. Overall, Apple has progressively moved from simpler voltage or resistance-based methods to more complex data communication systems to maintain control over the ecosystem and ensure a secure user experience

--- Updated Oct 6, 2024 ---

More GPT...

The Lightning connector uses a specific resistor configuration for authentication, but Apple does not publicly disclose the exact resistance values involved. However, the Lightning connector typically includes a 5-10kΩ resistor in the accessory circuitry to signal to the Apple device that it is an approved accessory.


Keep in mind that the complete authentication process involves more than just resistor values; it also includes digital communication protocols. If you're developing an accessory or working with Lightning technology, it’s essential to refer to Apple's official guidelines and developer documentation for accurate information on certification and design requirements.


In the Lightning connector, the authentication resistor is typically connected to the following pins:

• Pin 2 (Data +): This is one of the data pins used for communication.
• Pin 4 (Data -): This is the other data pin used for communication.

The resistor is usually placed between the accessory's VCC (power) and one of the data pins, often Pin 2. This configuration helps the Apple device recognize the accessory and determine whether it is authorized to connect.

-end GPT


For exact details and the best practices, it’s important to consult Apple’s official developer documentation, as the specifics may change or have additional requirements based on the accessory's design and functionality.

--- Updated Oct 6, 2024 ---

If you scope the data in logic analyzer mode you might be able to decode the response using a custom splitter cable and mimic it.

 

[Hawaslsh]

Thanks all for the replies! My word... there are a lot of website out there, with different resistor combinations in the D+ and D- lines for all sorts of devices and standards.

I just wanted to post what I found for anyone who googles it in the future. I ended up taking apart an extension cord, which had 2 USB outputs both capable of 2A. The cord worked on all my devices (no Samsung devices tested). So i copied the same resistor network from the extension cord.

Thanks again all!