PMP22477: PMP22477

Arvind Kumar

Part Number: PMP22477
Other Parts Discussed in Thread: TPS23730

Tool/software:

Hi TI Team,

I can see in feature "Primary Side Regulation(No Optocoupler)", but in given schematic secondary side regulation is also there in www.ti.com/.../tidma48a.pdf. Please provide reference schematic which will only support PSR not SSR. Or SSR with Optocoupler is an option here? Please explain the working of optocouplers in Page 3.

3 months ago

0 Arvind Kumar 2 months ago

Prodigy 60 points

Hi TI Team,

Can You reply on above query?

Regards,

Arvind

0 David Strasser 2 months ago in reply to Arvind Kumar

TI__Intellectual 2530 points

Hi Arvind,

The PMP22477 design does utilize PSR. The optocoupler is an optional circuit that provides adapter priority. When a 12V adapter is OR-d with the 12V PoE converter output, "PoE SELECT" should be pulled low, which turns on Q5, placing R54 in parallel with R58. This lowers the PoE output voltage, ensuring the adapter will provide the power.

Thanks, David

0 Arvind Kumar 2 months ago in reply to David Strasser

Prodigy 60 points

Hi David,

We are only using PoE, Not using Adaptor option so for that what things we need to remove?

And Do we need below circuit for our use please confirm we will not using any parallel PoE, only using provided reference solution 12Vout@3.8A.

Thanks.

0 David Strasser 2 months ago in reply to Arvind Kumar

TI__Intellectual 2530 points

Arvind,

You need the U3, U4 and U6 circuits show above. The remaining circuits on page 3 of the schematic provide optional input power limit and are not required (unless you want this function, it is mainly used for paralleling PoE inputs for higher power).

The circuits on page 1 are the typical PoE input functions. You will need these or something similar.

Since there is no adapter input, the circuits shown below from page 2 of the schematic are not needed.

Thanks, David

0 Arvind Kumar 2 months ago in reply to David Strasser

Prodigy 60 points

Hi David,

Why do we need U3,U4 and U6? I guess Working of TPH,TPL and BT pin to indicate PSE type, Please explain the purpose of these pins. And Why you are using optocouplers for these pins in reference schematic.

Thanks.

0 David Strasser 2 months ago in reply to Arvind Kumar

TI__Intellectual 2530 points

Arvind,

The TPH and TPL signals indicate the power allocated to the PD. The BT signal provides additional information about the PSE Type. I think the BT signal is optional, but check the IEEE802.3bt specification for details. TPH and TPL can also be provided serially over the TPL pin by tying SCDIS to VSS. These signals are referenced to RTN, which is on the primary side of the PD. The microprocessor they interact with is usually located on the secondary side of the PD, so isolation is required.

Please see sections 8.3.6, 8.4.1 and 8.4.5 of the TPS23730 specification for detailed information. Also reference the IEEE802.3bt specification for complete information.

Thanks, David