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

3.2.1.1 Blind Sink Support

The Fair Share Power Policy can be configured with an option to enable or disable Blind Sink Support. The FSP operation principal is the same with Blind Sink support, but the power distribution mechanism can vary depending on a Port Partner's Sink Capabilities.

Enabling Blind Sink Support allows the FSP Policy to take an additional step to determine if a connected Port Partner is a Blind Sink. As previously mentioned, the FSP always starts by initially advertising the Port Min Power and sends a Get Sink Capabilities request. If the Port Partner returns valid Sink Capabilities and is identified as a Good Sink, a new Source Capabilities message with PDOs that sufficiently meet the Sink Capabilities is sent back. However, when a Port Partner is identified as a Blind Sink, the FSP policy will offer Port Max Power instead if the second port is open and Per Port Guaranteed FSP if the second port is connected.

The following is how the TPS25772-Q1 identifies a Port Partner to be a Blind Sink:

  • Power reported from the first Sink Capabilities is less than the current contract power.
    • When a port connects to a Sink and it returns Sink Capabilities that is less than the initial contract power, the Port Partner is identified as a Blind Sink.
    • Inversely, when a port connects to a Sink and it returns Sink Capabilities that is higher than the initial contract power, the Port Partner is identified as a Good Sink. However, from the second Sink Capabilities onward, if the Port Partner reduces power from the current contract power, it will still be recognized as a Good Sink.
  • Power reported in the Sink Capabilities is less than the current Source Capabilities.
  • The Sink Capabilities is blindly copied from the Source Capabilities.
  • Sink Capabilities are not returned after a Get Sink Capabilities request.
  • Not supported is returned after a Get Sink Capabilities request.

The Table 3-4 highlights the Fair Share Power Policy operation and the difference when Blink Sink support is disabled and enabled.

Table 3-4 Difference Between Blind Sink Disable and Enable
FSP with Blind Sink Support DisabledFSP with Blind Sink Support Enabled
Initial Source CapabilitiesMinimum Port Power
Sink Capabilities HandlingHonor Sink Capabilities
Sink devices not reporting Cap Mismatch
Source sends Get Sink Capabilities request
Correct Sink Capabilities received Incorrect Sink Capabilities received
Offer power according to Sink Capabilities.When the second port is open, offer Port Max Power to the Blind Sink. When the second port is also connected: take the Blind Sink as a device whose Sink Capabilities is higher than the Per Port Guaranteed FSP and offer FSP to the Blind Sink as described in the 2nd and 3rd condition in Table 3-3.

When Blind Sink Support is enabled in the GUI either from the Simple Configuration view or Advanced Configuration view, an additional option to enable or disable "Max Power" becomes active. This will enable the charging port to treat every Port Partner as a Blind Sink and always offer Port Max Power regardless of behavior. In addition, when two Sinks are connected, Per Port Guaranteed FSP will always be advertised to Port Partners regardless of their Sink Capabilities. Some Sink devices return a Sink Capabilities message that is lower than what they are actually able to consume. The Max Power option can be adopted to support higher power charging for Sink devices such as these.

Blind Sink Support and the Max Power option can be enabled via the GUI's Simple Configuration view or Advanced Configuration view. See Figure 3-7 and Figure 3-8.

Section 5.2.1 provides example scenarios of FSP to better understand this policy's power distribution method when Blind Sink Support is enabled. For examples when Blind Sink Support and Max Power are both enabled, see Section 5.2.2.