STUSB4500 ATTACH pin use for detection of Cable attached to the Type C port

[AV.6]

Hi,

we ar designing a Tupe C Power Delivery and Communication on a single USB type C port. SO, if we are not connecting any device to the USB port , then the communication circuitry must be off and should not consume any power. and when the source is connected back in the port, the circuitry must wake from sleep and go back into normal mode.

This would be done without any complication, if we can use the ATTACH pin for detection of the cable connection and disconnection of the cable connection.

The reference design and the datasheet reference doesnt use such a pin for any purpose.

The datasheet pin description for ATTACH pin of STUSB4500 is given as detection for source to sink connection and used for communication purpose.

Please give proper idea if this pin can be used as a trigger for the above mentioned case.

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Thanks & Regards,

Akshay V

Kalkitech

[Gregory Go.]

Yes, you can use the ATTACH pin on STUSB4500, to know if the USB-C cable is attached or not.

The ATTACH pin is open-drain, so you need to add an external pull-up resistor.

Note that the ATTACH pin is used on STUSB4500 evaluation board (STEVAL-ISC005V1), when the board is mounted on STM32 Nucleo Board.

See some examples on the pictures below.

 

[AV.6]

Hi Gregory,

Thanks for the conformation.

How does the ATTACH pin works, and what are the inputs for enabling the ATTACH pin.

My guess is the CC pins are the ones triggering ATTACH pin output.

Can you please mention a brief note on the theory on how the ATTACH pin is working..?

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Thanks & Regards,

Akshay V

[Gregory Go.]

Yes, following the USB-C principle, the CC pins are used to detect the proper attachment to a USB-C source.

Note that if you connect 2 USB-C Sinks together, it is not considered as a good attachment scenario, so it won't detect the attachment.

The ATTACH pin is active low open-drain. 

So you need to add an external pull-up resistor.

Then:

- if ATTACH pin is high level => USB-C not attached.

- if ATTACH pin is low level => USB-C attached.

[AV.6]

thanks Gregory for the support

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thanks & regards,

akshay v