• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 62 subscribers
  • Views 399 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCD9090A: Soft-off sequencing in auto-enable mode

Peter Jancso
Intellectual 310 points
Part Number: UCD9090A

Hi, 

I would like to use UCD9090A for power up/down sequencing. 

Since UCD9090A is controlling all the CPU power on our board power-up sequencing shall start when main power rail (rail #9) is on.

Due to auto-on, I cannot use OPERATION or CONTROL mode, since the CPU cannot issue command or trigger the control pin yet.

Power off sequencing shall start, when power good off or undervoltage condition occurs on rail #9, but soft-off mode is not supported by Fusion GUI.

In chapter 4.7 of SLUA815 it is stated, that either using fault response to start sequence down or usage of pin selected state feature.

Is it recommended to define a GPO that indicates power good of rail #9 and use that to drive CONTROL pin?

Alternatively what else can be down to have both power up and down sequencing based on the voltage level on rail #9? 

Thank you in advance. 

Best regards, 

Peter

  • 0
    TI__Guru 58060 points

    Hi Peter

    If host can not issue commands or toggle any IOs,  there are three ways to do:

    if rails are configurued as AUTO, the only way to shutdown the rails is fault. you have to set up the proper fault response for rail 9 and setup fault shutdown slave so that other rails can be off when rail 9 has fault.

    if you have no plan to use fault shutdown approach. you can use pmbus_control via the following methohd

    A.if the POL of rail 9 can output a POWER_GOOD signa. you can connect this signal to PMBUS_CTRL of fUCD9090A and configure rails to CONTROL_PIN Mode.

    B. if the POL of rail 9 does not powe good output, you can use LGPO to write the signal to PMBUS_CTRL as described in the original post. there is no glitch filter in the power good detection. please take this into consideration.

    regards

    Yihe