TPS2378: When HDMI is inserted first, the TPS2378 is not powered.

user5010513

Prodigy 110 points

Part Number: TPS2378
Other Parts Discussed in Thread: TPS23754

1When RJ45 is inserted first,and then HDMI inserted, the TPS2378 is powered OK.

2When RJ45 is inserted first,and then Oscilloscope'GND inserted, the TPS2378 is powered OK.

3When HDMI is inserted first, and then HDMI inserted，the TPS2378 is not powered.

4When Oscilloscope'GND is inserted first,and then RJ45 inserted, the TPS2378 is powered OK.

We used the TPS2378+MP9928(DC-DC) to design.We believe that the external ground line (HDMI/Oscilloscope) interferes with the detection of the TPS2378, but our DC-DC is not isolated. Is there any way to solve this problem?

over 6 years ago

0 Darwin Fernandez over 6 years ago

TI__Mastermind 41770 points

Hi Yu,

Do you have schematic I can review? The HDMI circuitry should be referenced to RTN and note any capacitance on VSS to RTN can also contribute to failed detection (if the effective capacitance is above the CIN spec of the standard).

Regards,

Darwin

0 user5010513 over 6 years ago in reply to Darwin Fernandez

Prodigy 110 points

Sheet 09 LAN .pdf Sheet 17 POE.pdf

0 user5010513 over 6 years ago in reply to Darwin Fernandez

Prodigy 110 points

As my schematic,the HDMI circuitry is referenced to GND.I haved made the FB12/FB13/FB14 to 0R,but still not working.

0 user5010513 over 6 years ago in reply to Darwin Fernandez

Prodigy 110 points

I have reed the historical issues of TPS2378,my problem is like this.And the waveform of VDD with respect to VSS is same;

0 Darwin Fernandez over 6 years ago in reply to user5010513

TI__Mastermind 41770 points

Hi Yu,

Can you try inserting HDMI first and then measuring what the voltage is between VDD and VSS with multimeter (not scope)? Thanks!

0 user5010513 over 6 years ago in reply to Darwin Fernandez

Prodigy 110 points

Hi,

Insert HDMI first the voltage between VDD and VSS is 0.030V(no ETH in);

Insert the GND from PC first the voltage between VDD and VSS is 0.062V(no ETH in);

0 Darwin Fernandez over 6 years ago in reply to user5010513

TI__Mastermind 41770 points

Hi Yu,

When the HDMI is inserted, can you force a detection voltage between VDD and VSS (10V) and measure what the current is with a current meter? It should be ~400uA at 10V. If not, there must be some other load when HDMI is connected that is corrupting the detection by the PSE.

0 user5010513 over 6 years ago in reply to Darwin Fernandez

Prodigy 110 points

I have charge the electric circuit to TPS23754,But I do not know how to make the output to 5V/3A;can you help me ?

0 Darwin Fernandez over 6 years ago in reply to user5010513

TI__Mastermind 41770 points

Hi Yu,

The best approach for a Type 2 5V ACF design is to take the above EVM and modify it similar to PMP5818 which is an ACF 5V TI design. Please see below link. Thanks!

Power management

Power management forum

TPS2378: When HDMI is inserted first, the TPS2378 is not powered.