MPQ5031 — Sink reaction delay to reduced current; Extended Messages & VIF control; PS_RDY indication; GPIO3 “ISENS+” doc gap; LPS/Touch Current usage

[nfuzun]

Hello MPS Technical Support,

@Krishan.FAE @Edgar.FAE @adhish.FAE @MPSNow_Saurabh

We use the MPQ5031 USB-PD 3.0 Source Controller and need clarification on several items that affect both behavior and certification data.

1) Slow sink reaction after lowering current capability

• Initial advertisement: 20 V / 3 A.

• We reduce capability to 20 V / 2.25 A (update PDO current, then trigger new Source_Capabilities).

• The connected PC (sink) typically reduces its load after ~500–600 ms, and in some cases 1–2 s later.

• This feels far slower than typical PD transition expectations.
  Questions:

  1. Is there a recommended MPQ5031 sequence to make the sink react faster (e.g., <30 ms) when the source lowers available current?

  2. Since a true GotoMin control message does not appear to be available on MPQ5031, what is MPS’s official workaround (e.g., specific order of operations, resets, or limits)?

2) Extended Messages — how much can we customize?

• We understand Source_Capabilities_Extended / Status / PPS_Status are auto-composed by the PD engine, with some fields derived from registers (PDO volt/current, LPS, Touch Current, etc.).
  Questions:

  1. Which exact fields of Source_Capabilities_Extended are user-controlled via registers, and which are fixed by firmware?

  2. Is there any supported method to override or append vendor-specific data in Extended Messages, or are they strictly fixed to the internal template?

3) VIF (Vendor Info File) handling

• For USB-IF testing we prepare a VIF.
  Questions:

  1. Which VIF fields are effectively “fixed” by the MPQ5031 firmware (PD revision, identity, etc.) versus those that follow our PDO/LPS/Touch-Current register settings?

  2. Any MPQ5031-specific VIF template or guidance you recommend?

4) PS_RDY / contract state indication to host MCU

• We couldn’t find a direct “PS_RDY sent” or “contract valid” status bit exposed over I²C.
  Questions:

  1. Is there any register/bit/interrupt that explicitly indicates PS_RDY has been transmitted/acknowledged or that a new contract is active?

  2. If not, what is MPS’s recommended host-side method to infer readiness (e.g., monitor VBUS reaching target, current sense, a specific status field, etc.)?

5) GPIO3 function table shows “ISENS+”, but no description elsewhere

• The GPIO summary table lists ISENS+ as a selectable function for GPIO3, yet we don’t see configuration bits or description for this function in the GPIO control registers or text.
  Questions:

  1. Is ISENS+ actually available in production MPQ5031 silicon, or is it a reserved/internal/test function?

  2. If available, which register/field enables it, and what is the intended electrical connection and use case?

6) LPS and Touch Current fields (for certification data paths)

• We see LPS and Touch Current fields mapped into Source_Capabilities_Extended (via control register fields).
  Questions:

  1. Are these purely declarative (metadata for the sink / test tools), or do they influence any internal protection/limits?

  2. Can you share the exact bit-to-meaning mapping you expect customers to use (e.g., which codes correspond to “LPS compliant”, “<0.25 mA touch current class”, etc.) and the recommended way to verify them with a PD analyzer?

We’d appreciate official guidance, any app notes, and register-level details for the above—especially for accelerating the sink’s response to reduced current capability, and for clarifying the GPIO3 ISENS+ function and Extended-message/VIF controls.

Best regards,
Taha FUZUN
Embedded Software Developer — TCI Aircraft Interiors
nfuzun@tci.aero

[Krishan.FAE]

Hello Taha, apologies for the delayed response here. Let me look into this and get back to you soon.

[nfuzun]

Hello Krishan, is any update about topic?

[nfuzun]

@nfuzun

@Krishan.FAE @Edgar.FAE @adhish.FAE @MPSNow_Saurabh

Hello, is any update about topic?