MP8030 POE PD Application Question

DC-DC Power Converters
1

Dear Tier,

We are looking for a suitable PoE PD solution. Could you help us with some application-related questions?

  1. Why is there a distinction between high-side and low-side Hotswap in PD products? What are the advantages and disadvantages?

  2. Regarding the PoE handshake protocol issue, if both the external monitor adapter connected to the PD device and the PSE power adapter are grounded together Earth Ground, is there a risk of PSE-PD handshake failure? This consideration involves Hotswap switching between VSS and RTN or VDD and VBUS.

  1. If the PD side does not have an enclosure to guide surge energy to the Earth Ground for dissipation, and most PD devices become isolated (islanded) without this path to ground, how will surge energy be suppressed?
2

Hello Wenyung.kuo,

I will look into this and update you with a response.

3

Hi @eduardo.munoz ,

I would appreciate it if you could help me confirm these application issues.

BR,

Kuo

4

Hi @eduardo.munoz ,

Low side hotswap could potentially has a better CM impedance on the low side during detection and classification against the noise. Since the current sensor of PSE is on the low side too, low side hotwsap could be better detection/classification accuracy. Low side hotswap could also have a more robust gate driving capability since it refers the low side ground and no need for voltage pump to drive high side.

May I know you can advise low side hotswap with bt solution for us? thank you!

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5

Dear @eduardo.munoz or MPS support team,

1 week pasted, could you help us to advise? thank you!

6
  1. : Generally speaking, there is not much difference between the two; But in the application scenario mentioned in the second point, the anti-interference ability of High-side Hotswap is slightly weaker
  2. As shown in the figure below, taking High-side Hotswap as an example, in the customer’s application scenario, we suggest adding devices within the red box to reduce the risk of handshake failure
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  3. I need more information for this
7

Dear @eduardo.munoz ,

Got it, and thank you as well. If you could also provide the relevant timing waveform verification, it would help to confirm that the adding component activates the low-side reverse MOSFET through PG after the handshake protocol, Because I didn’t see a similar circuit in the MP8020 datasheet or the EVM.

BR,

KUO

8

Hello wenyung.kuo,

There are waveforms in the datasheet showing this and the flowchart also describes this.

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