TPS25740A: has bon sound when plugin Macbook pro

Dear TI support community / peer engineers

Please let me add to the detail - I am Andrew (Colt Advance) - we did more measurements with regard to the VBUS/GND voltage under this situation :

Our PS - A linear PS implemented with TL431 and power pass transistors - controlled by TPS25740A to TL431 resistor network.

1. This 25740A LPS (CA-PS ; as in Colt Advance PS) work fine with charging / powering the MBP (2 USBC socket version)
2. Issue occur when the MBP is fully charged and shut down (not sleep mode) - lid closed
3. When CA-PS is connected to the MBP under this condition - the VBUS on the USBC is 14.8V (Apple original PS would be 20.3V, another OEM PS is 14.8V) - MBP give out the first "Don" sound - this "Don" sound is expected and signal when PS is inserted and this is common
4. For Apple PS and OEM-PS would fall back to 5V (or near 5V) - MBP still in shut down mode
5. For CA-PS - the monitored VBUS (with DMM) drop to 0V and then back to 5V and then 14.8V - then the MBP give out the "Don" sound - signalling that the MBP is booting - and it would (if the lid is open) - this is different from Apple-PS and OEM-PS and is not expected.

Please let us know :

1. Has TPS25740A been used in any DFP PS for MBP ? Such product in production ?
2. Has this so call "corner case" been verified ?
3. Is LPS implementation causing any concern for interfacing (controlled by) TPS25740A ?

We are in a pre-production implementation stage and need to make up our plan ASAP - please let us know - Thanks.
Regards

Hi,

For my understanding, is this "Don" sound coming from the MacBookPro. It could just be the USB Type C cable enumerating once plugged into the port.

I'll take a look into this and will get back to you once there is an update.

Regards,

Jimmy Hua

Sounding once is expected - the MB is booted up though - which is not expected (Please see my added details posted 10 minutes ago - this is Andrew of Colt Advance.

Dear TI support community / peer engineers

Please let me add to the detail - I am Andrew (Colt Advance) - we did more measurements with regard to the VBUS/GND voltage under this situation :

Our PS - A linear PS implemented with TL431 and power pass transistors - controlled by TPS25740A to TL431 resistor network.

1. This 25740A LPS (CA-PS ; as in Colt Advance PS) work fine with charging / powering the MBP (2 USBC socket version)
2. Issue occur when the MBP is fully charged and shut down (not sleep mode) - lid closed
3. When CA-PS is connected to the MBP under this condition - the VBUS on the USBC is 14.8V (Apple original PS would be 20.3V, another OEM PS is 14.8V) - MBP give out the first "Don" sound - this "Don" sound is expected and signal when PS is inserted and this is common
4. For Apple PS and OEM-PS would fall back to 5V (or near 5V) - MBP still in shut down mode
5. For CA-PS - the monitored VBUS (with DMM) drop to 0V and then back to 5V and then 14.8V - then the MBP give out the "Don" sound - signalling that the MBP is booting - and it would (if the lid is open) - this is different from Apple-PS and OEM-PS and is not expected.

Please let us know :

1. Has TPS25740A been used in any DFP PS for MBP ? Such product in production ?
2. Has this so call "corner case" been verified ?
3. Is LPS implementation causing any concern for interfacing (controlled by) TPS25740A ?

We are in a pre-production implementation stage and need to make up our plan ASAP - please let us know - Thanks.
Regards

Hi Andrew,

Is it possible for you to provide a PD message from a PD analyzer? It would also help us if you can describe how many times the VBUS cycles (5V to 0V to 5V to 14.8V) in a 1 minute interval. This can give us a good clue on where the issue occurs. 

Regards,

Jimmy Hua 

Jimmy

We don't have this PD analyzer tool in house - would TI office around us has this tool ?

The 14.8V would stay for around 5 sec - then it would drop to 0V (this would stay briefly - less than 1 sec as observed on DMM) - then it would go to 5V (also briefly - less than 1 sec) - then go to 14.8V

The cycle repeat same as above.

Do you think this is normal and do you have a MBP (under the fully charged ; shut down condition) to test out with 25740A ?

Thanks.

This morning we reviewed the flow and has a hypothesis : 

The 14.8V to 0V (while Apple PS would go to 5V) - may mean under this situation either : 

- Our PS section is not dropping the 14.8V to 5V quick enough (So MBP detect a over-voltage situation so disconnect / shut down the PD VBUS 

- TPS25740A is receiving / interpreting the PD common to switch to 5V  - also causing the same disconnect / shut down of the PD VBUS 

Then the CA-PS switch up again to 14.8V 

Jimmy - can you give a email to send the video private ? 

Regards 

Hi Andrew,

Can you provide your email contact information? I would like to take this discusion offline from E2E.

Regards,

Jimmy Hua

Jimmy

Please send andrew@coltadvance.com

Thanks

Hi Andrew,

If I was able to answer your question, can you click the Verify Answer button?

Hi Jimmy

Sure - can you show me where the "Verify Answer" button location is ?