TPS26750EVM: Unexpected Behaviours.

Ming Guo

Part Number: TPS26750EVM
Other Parts Discussed in Thread: BQ25756EVM, , BQ25750EVM, BQ25756

Tool/software:

Hi, I am trying to demonstrate the following setup as shown in the image:

One TPS26750EVM with BQ25756EVM as a source to provide 24V 5A power. The power on the source comes from HV_SYS which is connected to a bench power supply.

One TPS26750EVM on the other side acts as a sink, sinking 24V 5A power. An EPR USB-C cable is used to connect them together.

The issues I am seeing are:

1) When HV_SYS = 5V, VBUS on source J4 and sink J4 were measured to be 3V. Doesn't look right to me.

2) When HV_SYS = 24V (or any voltage above 5V), the PP_EN and VBUS LEDs on the source flash at 1Hz rate, basically the VBUS output toggles between 0V and 5V every second. Seems like the system is constantly resetting.

I think I have programmed the boards correctly.

Would really appreciate any FAE support here.

Thanks!

4 months ago

0 Aya Khedr 4 months ago

TI__Mastermind 29932 points

Hi Ming,

Thank you for reaching out!

Could you share the jsons used with both EVMs?

Best Regards,

Aya Khedr

0 Ming Guo 4 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Could you please advise on how to export json file? As I am only able to export binary files.

0 Aya Khedr 4 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

Please see section 3.4.6.2 Exporting and Importing Settings from the EVM User's Guide on how to export a json file.

Best Regards,

Aya Khedr

0 Ming Guo 4 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Please find attached ZIP file for jsons for both sink and source.

1108.config.zip

Thanks!

0 Aya Khedr 4 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

Thank you for providing. I will test on my end and get back to you with feedback.

Best Regards,

Aya Khedr

0 Ming Guo 4 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Just wondering if you had any chance to recreate my setup on your end?

Thanks

Ming

0 Aya Khedr 4 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

My apologies for the delay on this one. I should be able to have feedback this week.

Best Regards,

Aya Khedr

0 Aya Khedr 4 months ago in reply to Aya Khedr

TI__Mastermind 29932 points

Hi Ming,

While reviewing the jsons provided, I noticed that the maximum sourcing power is 240W, but only 5V/3A SPR PDO is set.

According to the USB PD spec, when operating in EPR Mode, an EPR capable Source port should must offer 100W in fixed 20V.

I suggest generating a new json file based on the default setting in Transmit Source Capabilities register in the GUI and testing with the same setup.

Please let me know if the toggling still persists. Also, please capture PD logs if you observe abnormal behavior.

Best Regards,

Aya Khedr

0 Ming Guo 4 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Thank you for your reply. I tried the default settings in the GUI for the source and sink EVMs, but they didn't work. I am not able to capture PD logs as my PD analyzer has not arrived yet. Have you had the chance to recreate my setup on your bench? Could you please demonstrate how my physical setup, shown in the photo above, can deliver 24V from the source to the sink on your lab bench?

Best regards,

Ming

0 Aya Khedr 4 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

Could you share PD logs when you receive the analyzer?

In the meantime, I can reproduce on my bench and get back to you this week.

Best Regards,

Aya Khedr

0 Ming Guo 4 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Sure, I will share them.

One other issue I encountered today is not being able to flash the device.

I believe the following images show that I have ensured the connection is working, but the app still says disconnected when trying to flash. Do you have any idea why it is? I have tried unplug/plug and connect/disconnect many times and tried both on web browser and native application. It was working properly last week though.

0 Aya Khedr 4 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

Are you using the same PC that was used to flash the boards initially? Typically the EVM should show up as "TivaWare USB Serial Port" in Device Manager.

Best Regards,

Aya Khedr

0 Ming Guo 4 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Yes, I am using the same PC. I found that rebooting the PC solved the issue. Please let me know when your have the setup validated on your bench.

Thanks,

Ming

0 Aya Khedr 4 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

I am glad that flashing is working now.

I got the EVMs setup today and flashed them with your jsons and also saw the same behavior you described.

A couple questions/comments:

1- You mentioned wanting to negotiate a PDO of 24V/5A, but both jsons provided support up to 48V/5A. This means that the Sink will request the highest available PDO that the Source is offering which is 48V in this case. What voltage/current are you trying to achieve on both sides?

2- To negotiate a 24V contract, I set the maximum PDOs on both sides to 24V/5A and can see the negotiation occur successfully. See my jsons below.

Please let me know if you are also able to see this working normally on your end.

Fullscreen TPS26750_24V_5A_Source.json Download

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}

Fullscreen TPS26750_24V_5A_Sink.json Download

{
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0 Ming Guo 4 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Thank you for the feedback.

I tried your jsons but my EVMs still exhibited the same behaviour. Please see attached files for PD log. The CCGX3 file can be opened inEZ-PD Protocol Analyzer Utility (EZ-PD Protocol Analyzer - Infineon Developer Center) to allow you to see the detailed decoded messages. You can the source capability didn't mention EPR PDOs. VBUS goes down as soon as the source SPR PDOs were broadcasted.

A few things to note:

1. I used a known-good Apple PD Wall adaptor (20V 3A) as a source, and using a TPS26750EVM with your sink json as the sink. The EVM works well sinking 20V. So, I think we can confirm the sink is working.

2. How do I know if the BQ25756EVM is working properly? There is no indication on the board.

pd log.zip

0 Aya Khedr 3 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

Thank you for providing the PD logs. Which version of the Tool did you use to capture the PD logs?

Best Regards,

Aya Khedr

0 Ming Guo 3 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

I used this CY4500-EPR | CY4500-EPR EZ-PD Protocol analyzer - EZ-PD analyzer utility - Infineon Technologies with EZ-PD Protocol Analyzer Utility software version 4.2.0 on a Windows PC.

Best regards,

Ming

0 Aya Khedr 3 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

Thank you. I had downloaded a different version. I will re-download and get back to you.

Best Regards,

Aya Khedr

0 Ming Guo 3 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Are you able to gain any insights from the PD logs?

Best regards,

Ming

0 Aya Khedr 3 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

I noticed that the Sink did not send any Request message to the Source in the PD logs. Also, the VBUS voltage does look abnormal.

I suggest trying to test the Source PD+BQ board with a known sink device and see if it establishes a 5V contract. Ensure that there is I2C communication occurring between the PD and BQ. You can also measure the voltage on the VIN side of the BQ to ensure the expected output voltage is being provided.

Best Regards,

Aya Khedr

0 Ming Guo 3 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Thanks for the suggestion. I have tried it and the VIN of BQ is at 3.2V when voltage at HV_SYS is 5V. The negotiation didn't happen.

I also noticed when powering the PD EVM only through J3 and J8, the I2C traffic is not present. I2C traffic only presents when J4 or J6 is powered through.

I don't think we can afford debugging this EVM for indefinite amount of time, as we have project deadline to meet. Can I request a Purchase Order to buy a new set of 2x TPS26750EVM and 1x BQ25756EVM, and they should be programmed and tested to meet the 24V 5A delivery out of the box before shipping to us?

Thanks,

Ming

0 Aya Khedr 3 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Hi Ming,

Ming Guo said:
Thanks for the suggestion. I have tried it and the VIN of BQ is at 3.2V when voltage at HV_SYS is 5V. The negotiation didn't happen.

Could you connect the power supply on the BQ EVM (VIN) instead and ensure that the interposer board is tightly screwed in?

Ming Guo said:
I don't think we can afford debugging this EVM for indefinite amount of time, as we have project deadline to meet. Can I request a Purchase Order to buy a new set of 2x TPS26750EVM and 1x BQ25756EVM, and they should be programmed and tested to meet the 24V 5A delivery out of the box before shipping to us?

I completely understand. The out-of-box firmware will not be set to 24V/5A since this is not a standard EPR PDO. But, the jsons provided should be able to meet 24V/5A.

Best Regards,

Aya Khedr

0 Ming Guo 3 months ago in reply to Aya Khedr

Prodigy 120 points

Hi Aya,

Aya Khedr said:
Could you connect the power supply on the BQ EVM (VIN) instead and ensure that the interposer board is tightly screwed in?

I tried this and it was not working.

However, I found that source PD EVM working standalone without BQ can delivery 5V3A when programmed with json in the attachment. PD log is also attached. The VBUS measured at sink PD EVM is 5V which is expected, but sink PD EVM PPHV is about 2V. Why would this be? I then swapped the sink to a known-good 5V sink device and the negotiation happened and it was powered on properly.

I think this also means the issue likely comes from BQ. I think I will buy a new BQ25756EVM. There are BQ25756EVM and BQ25750EVM. What are the differences? When I click Order the EVM on ti.com in BQ25756 Evaluation Module User's Guide (Rev. D)? It takes me to BQ25750EVM.

Aya Khedr said:
The out-of-box firmware will not be set to 24V/5A since this is not a standard EPR PDO.

What is the setting in the out-of-box firmware? I just need to confirm 1x out-of-box TPS26750EVMcan do 240W (48V/5A) Source and 240W (48V/5A) sink with 1x out-of-box BQ25756EVM . If not, please elaborate.

Best regards,

Ming

0 Aya Khedr 3 months ago in reply to Ming Guo

TI__Mastermind 29932 points

Ming Guo said:
There are BQ25756EVM and BQ25750EVM. What are the differences?

These EVMs are for different BQ parts. The TPS25756 pairs with the BQ25756.

Ming Guo said:
What is the setting in the out-of-box firmware? I just need to confirm 1x out-of-box TPS26750EVMcan do 240W (48V/5A) Source and 240W (48V/5A) sink with 1x out-of-box BQ25756EVM . If not, please elaborate.

This is highlighted in section 2.3 in the EVM User's Guide:

Also, please refer to the following image to ensure proper jumper configuration on the BQ25756.

Best Regards,

Aya Khedr

Power management

Power management forum

TPS26750EVM: Unexpected Behaviours.