TPS25740: Reference design utilizing the LM5175

Hi Larry,

Since it has been a while, i'm going to go ahead and close this thread. If you encounter any issues, feel free to re-open this thread, or start a new one. Thanks for choosing TI parts for your design :-)

Donovan,

Still having issues with my design, I can send you my schematic which follows your application circuit in the data sheet for he TPS25740.  Resolved the issue with the phone only charging when the USB Type-C connector one way, it was a bad solder joint on the USB Type-C connector.  The issue I am having now is that I can plug my older Droid Turbo and it charges fine around 1.25 Amps which is about right.  But when I plug in a couple of new tablets, one tablet will continuously drop out and reconnect I can see my input power supply current increase briefly then drops back down to zero.  This continues as long as the device is plugged in.  The other tablet I plug in does not seem to charge at all.  I purchased TPS25740-741 EVM and I do not see this issue with the eval board.  Pulling my hair out since I've gone over the Eval board schematic and my schematic and don't see why this is happening.  Any help would be appreciated since I'm on a deadline and the customer is pushing to release the design.  Attached is a PDF of my schematic any help would be appreciated.

USB 5V_12V_20V Power (Rev C).pdf

Sent schematic to Donovan to review, still having issues with the design using the TPS25740.

Hi Larry,

Could you send scope shots of VBUS, CC, and current through VBUS when these tablets are connected?

Thanks,
Donovan

Yes I can will have to get the tablets back in the office.

Donovan,

See attached document with pictures.  It was difficult getting a current reading on the tablet due to the fact it was turning the Vbus on and off.  Also in you documentation you specify pins 9 and 10 as NC (No Connection) but then show them connected to ground.  What happens if these are not connected to ground.  On my layout these were not connected to ground but I tried modifying the board to get these connected to ground, pretty difficult since the pins are hard to get to.  Let me know if you have some recommendations or solutions to my problem.

TPS25740 signals.pdf

TPS25740 signals Ver2.pdfDonovan,

A couple extra pictures at the end of the document showing CC1, CC2 and Vbus when Verizon tablet was connected to the TPS25740EVM-741 evaluation board

Thanks Larry. I'll take a look and see if I can figure out what is wrong.

Regards,
Donovan

Hey Larry,

Have you tried a different Type-C cable?
Have you tried any other Type-C devices?
Does it make any difference if the cable is plugged in first, then the tablet or plugging in the cable while the tablet is connected?
Is it possible to get a single scope capture showing CC1, CC2, VBUS, and VBUS current? There could be an issue with in-rush current.

Thanks,
Donovan

Donovan,

I tried the same cables on the development board and they work with the development board.  I've tried both the Type-C to Micro-USB B cable and the Type-C to Type-C cable.  The Type-C to Micro-USB B cable works both on the evaluation board and my design.  The Type-C to Type-C does not work on my board but works on the evaluation board.  As noted in the previous reply with the pictures plugging in the Type-C to Type-C cable with nothing plugged in at the other end the CC1 and CC2 signals don't change on the evaluation board or my design.  When I plugged the Verizon tablet in it works with the evaluation board, on my board I get the power switching on and off per the scope screenshots.

I will try and get some snap shots of CC1, CC2, Vbus and Vbus current.  I will have to get a current sensing IC in for the Vbust current, since the resistor in the system .005 ohm is so small it's difficult getting a signal across it.

Donovan,

The cables work on the evaluation board (TPS25740EVM-741) as I mentioned and the Type C device works on the evaluation board.  Does not make a difference if the cable is plugged in first then the tablet.  I also have another board that with nothing plugged into the USB Type-C connector I'm seeing 4.48 volts on both CC1 and CC2.  Typically what I was seeing and whats on the evaluation board is 2.7 volts when nothing is plugged into the USB Type-C port, what would cause both CC1 and CC2 to be at 4.48 volts?