SLVAFG6A December   2022  – November 2023 TPS25762-Q1 , TPS25772-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Terms and Abbreviations
  5. 2 SPM Engine Overview
  6. 3Multi-Port Power Allocation Policy
    1. 3.1 Assured Capacity Policy
    2. 3.2 Shared Capacity Policy
      1. 3.2.1 Fair Share Power Policy
        1. 3.2.1.1 Blind Sink Support
    3. 3.3 Hybrid Mode
  7. 4Power Foldback Policy
    1. 4.1 Thermal Foldback Operation
    2. 4.2 Engine Start or Stop Transition Management
      1. 4.2.1 Engine Start or Stop Power Foldback Operation Example
  8. 5Multi-Port Power Allocation Policy Examples
    1. 5.1 Assured Capacity Policy Example
    2. 5.2 Fair Share Power Policy Example
      1. 5.2.1 FSP Policy Example – Blind Sink Support
      2. 5.2.2 FSP Policy Example – Blind Sink Support with Max Power
    3. 5.3 Hybrid Mode Example
  9. 6References
  10. 7Revision History

5.2.1 FSP Policy Example – Blind Sink Support

This section provides examples of Fair Share Power Policy's power distribution with Blind Sink Support enabled for both ports and in the event of a port connecting to a Sink that fails to return Sink Capabilities correctly. Note that the Max Power option is not enabled in these examples. Table 5-6 shows the SPM Engine parameters used in this section's example. The FSP Parameters shown in Table 5-7 are used in the Fair Share Power Policy's power distribution to achieve FSP between two Sinks.

Table 5-6 SPM Engine Parameters - FSP Example with a Blind Sink
SPM Engine Parameters Configuration Description
Total USB VBUS Power (System Max Power) 75 W Total system power capacity allocated for Port A and B
Port A Max Power 60 W Maximum Port A Power
Port B Max Power 60 W Maximum Port B Power
Port A Min Power 15 W Minimum Port A power
Port B Min Power 15 W Minimum Port B power
Shared Mode FSP with Blind Sink Support Port Max Power is offered to Blind Sinks
Table 5-7 Fair Share Power Policy Parameters
Fair Share Power Policy Parameter Value Description
Equally Divided Shared Power (75-(15+15))/2=22.5 W Shared power for each port that can be distributed if available: (Total VBUS power – Sum of Port A and B's Min Power)/Total number of ports
Per Port Guaranteed FSP 15+22.5 W=37.5 W Port Min Power + Per Port Equally Divided Shared Power = Per Port Guaranteed FSP

Three example scenarios of Fair Share Power Policy operation (when Blind Sink Support is enabled) are shown in Table 5-8. The table format in this section is structured differently to show how Blind Sinks are handled and supported by the SPM.

Table 5-8 FSP Example with Blind Sink Support
Port A Port B SPM Operation Description
Initially Allocated 15 W 15 W Min Power is initially allocated for Port A and Port B.
Scenario 1: Port A connects to Good Sink #1. Port B is unconnected.
Source Cap 1 15 W The first Source Cap is sent to Port A's Sink with Port Min Power.
Sink Request 15 W Grant 15 W to Port A.
Sink Cap 45 W Source sends Get Sink Cap message to Port A and max 45 W Sink Cap is returned.
Source Cap 2 45 W A 45 W Source Cap is sent again based on Sink Cap.
Sink Request 45 W Port A Sink requests 45 W.
Power Distributed to Sink 45 W 45 W distributed to Port A Sink.
Scenario 2: Port A is replaced with a Blind Sink. Port B is still unconnected.
Source Cap 1 15 W The first Source Cap is sent to Port A's Sink with Port Min Power.
Sink Request 15 W Grant 15 W to Port A.
Sink Cap 15 W Source sends Get Sink Cap message to Port A. Source Cap = Sink Cap is returned. Port A Sink is identified as a Blind Sink.
Source Cap 2 60 W A Source Cap is sent again with Port Max Power.
Sink Request 60 W Port A Sink requests 60 W.
Power Distributed to Sink 60 W 60 W is distributed to Port A Sink.
Scenario 3: Port B connects to Good Sink #2. Port A continues to deliver 60 W to Blind Sink.
Source Cap 1 15 W The first Source Cap is sent to Port B's Sink with Port Min Power.
Sink Request 15 W Grant 15 W to Port B.
Sink Cap 20 W Source sends Get Sink Cap message to Port B and max 20 W Sink Cap is returned.
Source Cap 2 55 W 20 W Port A Sink's required power is less than the Per Port Guaranteed FSP. Port B's required power is higher. The SPM distributes power to the Port A's Sink requesting lower power and the remaining power to Port B's Sink.
Sink Request 55 W 20 W Port A Sink requests 55 W and Port B Sink requests 20 W.
Power Distributed to Sinks 55 W 20 W 55 W distributed to Port A Sink. 20 W distributed to Port B Sink.

Figure 5-5, Figure 5-6, and Figure 5-7 show the PD negotiation flow of the FSP examples from Scenario 1, Scenario 2, and Scenario 3 of Table 5-8, respectively.

GUID-20221004-SS0I-NK8J-4VRV-PVFSVXLSMZ1L-low.png Figure 5-5 FSP Negotiation Flow with Blind Sink Support – Scenario 1
GUID-20231018-SS0I-KMXG-4F8L-8VL5KX1TJK6H-low.png Figure 5-6 FSP Negotiation Flow with Blind Sink Support – Scenario 2
GUID-20231031-SS0I-SCLP-VGXT-QKBXVCBFJPNT-low.png Figure 5-7 FSP Negotiation Flow with Blind Sink Support – Scenario 3