UCD90160 - 16 rails and ON / OFF sequencing of two groups

Question 1:  You can define a GPI under the Pin Assignment tab of the Configure page, I called this one Enable #1.

Then return to the Vout Config tab and the pin will show up as avaliable for use as an On and/or Off dependency.

Question 2:  The operation of PMBus_CNTRL can't be split for turn-on vs turn-off which will make 1-2-3 turnon and 3-2-1 turnoff sequence type impossible, however defining an individual GPI as an enable does allow this functionality.

Question 3:  Looks like you have terminology reversed, Given the dependencies defined in your question, if Rail_3 was first disabled rail then nothing would happen to Rail_1 or _2.  Given your definition, if Rail_1 was dependent on CNTRL line it would turn off at 5ms followed by Rail_2 at 10ms and Rail_3 at 15ms.

For clarity, to make sure we are seeing things the same, below is screen shot of Rail_1 Sequence Off Dependency for Rail_2.

So when Rail_1 goes below its PG level, Rail_2 will be sequenced off.

Dear Brad,

Thank you for the answers.

I haven't been specific in my question 2 and unfortunately I don't fully follow - need further clarification.

For simplicity - design uses 10 rails - All my rails are "CONTROL pin only".

2a) Every rail has equal "turn ON delay" = 10ms, rail X-1 is rail's X dependency, then PMB_CNTRL changes from LOW to HIGH will create Sequence ON where rail 1 starts first at time=10ms, rail 2 starts at time=20ms, rail 3 starts at time=30ms, and so on. Correct?

2b) Rail X has "turn OFF delay" 10ms shorter then rail X+1 (rail10 "turn off delay" 10ms, rail9 "turn off delay" 20ms, rail8 "turn off delay" 30ms, ... ), there are NO "turn off" dependencies, when all rails are operational (all rails are "power good") then PMB_CNTRL changes from HIGH to LOW will create Sequence OFF where last rail10 is disabled first at time=10ms, rail9 disabled at time=20ms, rail8 disabled at time=30ms, and so on, creating reverse to the sequence described in 2a. Correct?

2c) What happens (with setup described in 2a and 2b) if in the middle of the sequence ON process PMB_CNTRL changes from HIGH to LOW for example 5 rails have been sequenced ON, still 5 rails should be sequenced ON but PMB_CNTRL changes to LOW? Already sequenced rails will be sequenced OFF in reverse order?

2d) On top of the setup described in 2a and 2b every rail have every other rail as "Fault shutdown slave" and every rail have fault responses enabled as follows: Vout UnderVoltage and Vout OverVoltage enabled - response "Shutdown with delay" - "do not restart" - deglitch enabled = 5ms and Re-Sequencing enabled then when all rails are operational (all rails are "power good") and one of the rails goes below / above Under / Over Voltage Fault threshold for longer than deglitch limit will cause Sequence OFF of all rails in reverse sequence to the sequence ON sequence pause for period defined as "Time between Re-Sequence" and then Sequence ON? Correct?

Thank you very much for all your time.

Best regards,

Adam

There was an error in my Question 2 response which I've updated, UCD90xxx sequencers use Sequence OFF Dependencies which require all depencencies to be met before rail turns off while my answer was based off the UCD92xx controllers Turn-off Dependencies which only require one of the defined sources to go away to cause the rail to shutdown.

Therefore, PMBus_CNTRL pin can be used to initiate 1-2-3 turn-on and 3-2-1 turn-off with proper Sequence Off Dependency settings.

Answers for remaining questions will be posted shortly.

Hi Adam,

To address your questions:

2a)  Turn-on dependencies are event based while turn-on delays are time based.  If you have turn on dependencies in your configuration (and it looks like you do) then the delay timer to enable the rail will not start until the previous rail has passed its Power Good on threshold.

Say Rail #4 is turn on dependent on Rail#3 pictured above.  Right when Rail #3 is enabled and is in the process of turning on, the turn on timing of 10ms for Rail #4 has not started yet.  Once the sequencer sees that the voltage rail has gone above 2.25V through the MON pin assigned to that rail,  the turn on delay will start.  You need to incorporate the power up time of each rail into your timings if you have turn on dependencies.

2b) That is correct because you do not have any turn off dependencies.  You do not have to wait for the preceding rail to go below its Power Good Off value before the Turn Off Delay is enabled.  

2c) Yes they will be off in reverse order if you have it set that way in their turn off sequence.  One thing to keep in mind here...say you have the scenario you mentioned for powerdown sequence - rail 10 @ 10ms, rail 9 @ 20ms, rail 8 @ 30ms, etc...if the PMB_CNTRL is switched low right after rail 5 is powered UP, it will not be powered down until its power-down delay of 60ms is done.

2d)  Yes they will sequence off in the power-down sequence timing, wait the time set in "Time Between Re-Sequences" found in the "Other Config" tab in the GUI and then resequence.

Hope this helps.

Regards,

Dan

Hi Dan,

Perfect, very helpfull and to the point.

All quenstionas answered.

Best regards,

Adam