TPS2378: TPS2378 No power supply problem

dave lan

Part Number: TPS2378
Other Parts Discussed in Thread: TPS23861,

HI SIR/ma

Now the customer has made a set-top box solution with POE, using TI's TPS2378.Now the problem is that when set-top box‘s HDMI connection to the backend display, TP cc-link POE switches (PSE scheme is TPS23861) is not power, but using TENDA switches (PSE scheme is IP804) and broadcom switches (PSE scheme is broadcom), the two switches can be power supply.When the HDMI cable is not connected, each switch can supply power to the set-top box normally. Please help to analyze. What caused it?

POE(1).pdf

over 7 years ago

0 Thomas Lewis over 7 years ago

TI__Expert 5615 points

Dave,

Thank you for reaching out to us and initiating a discussion. From your brief post here, there is a chance that we may need to take this offline and dig deeper into the system to reach root cause.

I am assigning this post to a few experts and we will work to close it. My initial question to you is this: Has the set-top box undergone SIFOs and/or UNH-IOL compliance and/or interoperability testing? If so, do you know the outcome of those test(s)?

Thank you for assisting in this matter,

0 Darwin Fernandez over 7 years ago in reply to Thomas Lewis

TI__Mastermind 41760 points

Hi Dave,

Also, what first catches my eye on the schematic is there is a lot of cap at the PoE front end (note the standard requires up to 0.12uF). What value is C130 (it should be ~1000pF)? C131 should be removed, C85-C88 should be 0.01uF and not 0.1uF.

In addition, can you take a waveform of VDD with respect to VSS that shows the detection and classification (waveform similar to Figure 19 of the TPS2378 datasheet)?

Thanks!

0 user5157625 over 7 years ago in reply to Darwin Fernandez

Prodigy 120 points

The correlation parameter modulation is the same as the EVM board, but still not.

Customer only give OTT (TPS2378 + MP2494) under the condition of power supply, several switches can be normal power supply,When OTT's HDMI is first linked to the monitor, TP - LINK switch（In semi auto mode）can't power supply, and we TPS23861evm can normal power supply.TPS2378.docx

0 Darwin Fernandez over 7 years ago in reply to user5157625

TI__Mastermind 41760 points

Hi user,

If HDMI is having issue, can you also send schematic of how the HDMI connector is connected to the board?
Did you try yet the cap changes I recommended?

0 dave lan over 7 years ago in reply to Darwin Fernandez

Intellectual 520 points

hi Fernandez,

I have changed the capacitors of these several places, or the same question.

Could you please tell me your email address?

I will give you the schematic diagram.

thsnks~~~

0 Darwin Fernandez over 7 years ago in reply to dave lan

TI__Mastermind 41760 points

Hi Dave,

Please use dfernandez@ti.com

Thanks!

Power management

Power management forum

TPS2378: TPS2378 No power supply problem