10.36 (F6h) SEQ_CONFIG (MFR_SPECIFIC_38)

This Read/Write Block command configures the sequencing dependencies and enable pin for a given rail.

Features include:

• Sequencing – Configures interdependency between how voltage rails are enabled/disabled
• Fault Slaves – Configure slave pages which also shut down when a fault occurs
• Enable Pin – Identifies the enable pin, and its operating characteristics.

NOTE

All configurations done with the GPI_CONFIG command must be done before writing this command.

NOTE

When this command is written, the enable pin for the rail is de-asserted. Then the state of the rail is reevaluated. If it is determined that the rail should be on, the enable pin is asserted.

The turn on condition for each page can depend on the state of several other pages and/or input pins. The same pages and pins also may be used to control multiple pages. The GPI and Page dependencies (Sequence On Dependencies) define a set of conditions which allow a page to turn on when met. Note that the logical AND of all conditions must be met. Once the page is on, these dependencies have no further effect on the operating status of the page. Specifically, they do not cause a page to turn off.

Sequence On Dependencies work in parallel with the PMBus defined mechanisms used to enable an output. That is, both the Sequence On Dependencies and the PMBus mechanism must be satisfied. For example, if the page responds to an OPERATION command, until ON is specified by the command, the page remains off even if all of the sequencing Sequence On Dependencies are met. Further, the order in which they are met is irrelevant; the OPERATION command can be issued first and then the sequencing requirements, when met, turn on the output, or the sequencing requirements can be met first in which case the page would wait for the command. In the ON_OFF_CONFIG command a “None” setting, is still subject to the specified Sequence On Dependencies.

Turn on delay (TON_DELAY) is applied after the page has been commanded on and Sequence On Dependencies are met.

Unless the rail is instructed to turn off immediately, these same comments apply to the Sequence Off Dependencies – they must be met before the rail is turned off, the turn off delay (TOFF_DELAY) is applied after the dependencies are met, etc.

After a fault, the PMBus specification declares that an OFF/ON sequence occur before the rail is allowed to restart. Note that the toggle of sequencing pin is interpreted to meet this requirement. For example, consider a page that responds to the CTRL_PIN and has a Turn-On Dependency which shuts down due to a fault. A toggle low then high on either the CTRL_PIN or the sequencing pin is sufficient to restart the page.

NOTE

Some tables in the following subsections assume that the device supports 16 rails (0 to 15). For a given device, this may not be the case. The interpretation of this information should be adjusted for the correct number of rails.