Guidance for USB type-C Power Role Swap Design

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SkOl_4094796
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I'd like to create a USB type-C power delivery hub with two USB type C receptacles and one USB A receptacle (for power delivery only).  One USB type-C receptacle would be used to connect to charger (wall wart or 12V dc charger for example) and the other USB type-C receptacle would be connected to an Ipad Pro 11.  The one USB A receptacle would be connected to a 5VDC fan (max 750mA at startup/400mA normal operating).  I'd like the fan to be powered off of the charger or, when the charger is unplugged, be powered off of the Ipad.  I'm struggling to find a straightforward solution.  Any help is appreciated.

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RajathB_01
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Hi Skyler,

Here is an initial block diagram and some description of how your system would be like. Please refer to attachment.

I am assuming the Type-C receptacle that connects to wall wart / charger in scenario #1, is never used in #2.

Let me know if you need more details / corrections.

Regards,

Rajath

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RajathB_01
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Hello,

Some clarifications before suggesting a design -

1) There is no requirement for data path.

2) Is the DC fan operating all the time, when either of the type-c ports is connected?

3) Is the wall-wart / charger always PD capable?

Please confirm these for further analysis.

Regards,

Rajath

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Hi Rajath,

Your first two assumptions are correct.

For the third assumption, if I understand correctly, we would like to be

able to use any wall charger with or without the power delivery capability.

Thanks,

Skyler

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Skyler,

One last question, do you want the Type-C receptacle that connects to wall wart / charger in scenario #1, to source power in scenario #2? Or is it never used in #2?

Apart from that let me know if you are interested in a single PD controller design or dual controller design for the two receptacles.

Regards,

Rajath

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RajathB_01
Moderator
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250 replies posted 100 replies posted 50 replies posted

Hi Skyler,

Here is an initial block diagram and some description of how your system would be like. Please refer to attachment.

I am assuming the Type-C receptacle that connects to wall wart / charger in scenario #1, is never used in #2.

Let me know if you need more details / corrections.

Regards,

Rajath

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Thanks for the diagram Rajath.  You are correct that P1 does nothing in scenario 2.  As far as a single or dual PD controller, I'm looking for simplicity in the final design so my inclination is to use a single PD controller.  I'm open to use two of there are some advantages I'm not considering.

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Hi Skyler,

You can choose to have single PD controller, as I have mentioned in a note in the attachment, you will be only able to sink 15 watts on P1.

This will limit the sourcing capability on P2, since the DC fan is also going to take some part of this 15 watts. You will end up with less than 15 watts to charge your ipad.

A two PD controller approach will be more generic and thus will adapt to different kinds of devices and scenarios, along with providing more power on P2.

Regards,

Rajath

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