TPS23861: TPS23861 I2C issue

AndongSun

Part Number: TPS23861

Hi expert:

Attachment is our schematic diagram, we use two TPS23861 for the 8 port PSE ,the two TPS23861 I2C address is 0x20 and 0 x28 respectively. However, when we read the register, all the value are 0xFF.Then we made a polling, found that only read the I2C address 0 x00 register.

Please help to check the sch. Any Suggestions will be appreciated.

TPS23861_POE+2.pdf

Best regards

over 6 years ago

0 Penny Xu over 6 years ago

TI__Genius 15685 points

Hi Andong，

First I want to isolate HW and SW issues. Please do the following to help me analyze.

Send me a waveform including VPWR(48V), VDD(VCC_3V3), and RESET(PSE RESET) during system power on.
Without any host control, after power up, connect a PD to a PSE port and see if the PD can be turned on or not.

Thanks,

Penny

0 AndongSun over 6 years ago in reply to Penny Xu

Intellectual 600 points

Penny,

Thanks for your reply.

1. Since our oscilloscope has only two channels, we have captured them twice, the first channel is VPWR and VDD, and the second channel is always Resetn. The picture is in the attachment.

2. PD power supply is normal.

Best regards

0 Penny Xu over 6 years ago in reply to AndongSun

TI__Genius 15685 points

Hi Andong,

Looks like the power on sequence is not met. The RESET pin should be kept low before Vpwr reaches to UVLO(28V max). Please ask your customer to review this app note and modify the hardware. Thanks.

Best regards,

Penny

0 AndongSun over 6 years ago in reply to Penny Xu

Intellectual 600 points

Hi Penny，

Thanks for your support.

I will ask my customer to modify the hardware according to the 'TPS23861 Power-on Considerations'.

Best regards

Power management

Power management forum

TPS23861: TPS23861 I2C issue