TPS23861: TPS23861 Detection waveform at drain not correct

Mikha Waghmare

Part Number: TPS23861

Hi Expert,

I am trying to implement a Single Port PSE using the TPS23861. I want to operate the TPS23861 in Auto Mode. I am not being able to get the PD Detection waveform at the Drain pin of the IC. Instead of getting the pulses I am getting a constant 46V. The other voltage readings for the IC are given below:

VPWR- 55V - 53.6V

VDD- 3.6V - 3.12V

The waveforms for DRAIN to GND and VPWR to DRAIN are attached to this post. Also attached is the expected waveform at the DRAIN. /cfs-file/__key/communityserver-discussions-components-files/196/7268.Drain-waveforms.zip

Please let me know how I can debug this problem.

Thanks.

Mikha.

over 6 years ago

0 Penny Xu over 6 years ago

TI__Genius 15685 points

Hi Mikha,

Can you send me your schematic for review? I need a full schematic including the RJ45 connector. Thanks!

Best regards,

Penny

0 Mikha Waghmare over 6 years ago in reply to Penny Xu

Intellectual 410 points

Hi Penny,

Thanks for your immediate reply. I have attached the schematic of the circuit including the RJ-45 connector here.

0 Penny Xu over 6 years ago in reply to Mikha Waghmare

TI__Genius 15685 points

Hi Mikha,

Can you try removing the LED connected to R20 and see if you can get correct detection waveform? Thanks.

Best regards,
Penny

0 Mikha Waghmare over 6 years ago in reply to Penny Xu

Intellectual 410 points

Hi Penny,

I removed the LED connected to R20. It increased the voltage at the Drain pin but the detection signal is still not there. I have attached the Drain to Ground and VPwr to Drain waveform. Is it possible that the TPS23861 Power On sequence is not correct? or is it a problem with the Vdd supply?

Drain Waveforms: /cfs-file/__key/communityserver-discussions-components-files/196/Drain-2-Waveform.zip

Thank you.

Regards,

Mikha.

0 Penny Xu over 6 years ago in reply to Mikha Waghmare

TI__Genius 15685 points

Hi Mikha,

Did you program the TPS23861 through I2C, especially register ox11? The Vpwr -Drain waveform doesn't look correct to me. Can you check the Vpwr-GND waveform? Looks like the 54V rail is oscillating. Thanks.

Best regards,
Penny

0 Penny Xu over 6 years ago

TI__Genius 15685 points

Hi Mikha,

Did you solve your problem? If not, can you send me the information I requested for further debug? Thanks.

Best regards,
Penny

0 Mikha Waghmare over 6 years ago in reply to Penny Xu

Intellectual 410 points

Hi Penny,

Yes the problem is solved. I had wrongly programmed the IC so after replacing the IC it is working.

Thanks for the help.

Regards.

Mikha

Power management

Power management forum

TPS23861: TPS23861 Detection waveform at drain not correct