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UCD9090A: Initial sequencing does not appear correct

guy lemire
Intellectual 970 points
Part Number: UCD9090A


Hello,

I am using a ucd9090a to monitor and sequence 7 rails.

As a start, I have a master 3.3V that is powered up

1) I monitor the rail. once the rail reaches 3.3V -5% I declare power good

2) I then enable my second rail once this power good logic occurs + 10000ms delay. However I do not see this sequencing occur. I have included my project in this thread. It seems to be fairly straight forward, but I do not see a delay between the two rails.

regards,

GuyUCD9090A @ PMBus Address 104d Project_0204_v1.xml

  • 0
    TI__Guru 66920 points

    Hi

    Please refer the attached file for the sequencing.

    UCD9090A @ PMBus Address 104d Project_0205_v2.xml

  • 0 in reply to yihe
    Intellectual 970 points

    Hi Yihe,

    thank you for the update. I am trying to use either operational mode or PMBus CTRL to enable the sequence so that I can monitor my PCB as I bring up the power. I updated the project file to include an operational pin setting for the 5V enable. But I still do not see the %V_EN toggle when I turn the operation command on/off.UCD9090A @ PMBus Address 104d Project_0205_v4.xml

    Regards,

    Guy

  • 0 in reply to guy lemire
    TI__Guru 66920 points
    Control pin/operation comand is only used to control the ENABLE pin of the rail, Logical controlled GPO is not controlled by control/operation command.
    Please use the sample project file provided in my previous post and add the operation control to the 5V rail.
    Regards
    Yihe
  • 0 in reply to yihe
    Intellectual 970 points
    Hi Yihe,
    I set the 5V rail ro oeration only but i still do not see the rail respond when i turn on/offried the image that you sent me and I do not see the 5V enable pin toggle even when I set the operation control to the 5V rail.

    There must be something I am missing. I should be able to turn this rail on and off manually.

    Regards,
    Guy
  • 0 in reply to guy lemire
    TI__Guru 66920 points

    Please refer the attachment, you will see pin 26 toggle when change the operaton command

    Regards

    Yihe

    UCD9090A @ PMBus Address 104d Project_0205_v5.xml

  • 0 in reply to yihe
    Intellectual 970 points

    Hello Yihe,

    using the rail enable did help. thank you for your help. I addesd several other rails and I am seeing a discrepancy between what the tool sequence page shows and what I measure on my PCB. For some reason the 1V8 rail appears to start to rise before the VCCINT rail, which it should not do.

    UCD9090A @ PMBus Address 104d Project_0206_v1.xml

    Regards,

    Guy

  • 0 in reply to guy lemire
    TI__Guru 66920 points

    Hi Guy

    Why is the logical controlled GPO used for rail enable? will you consider the ENABLE function like what demonstrated in the sample file?

    Could you probe the voltage on the both VCCINT and 1V8 and the EN signals respectively? you may have some leakage so that VCCINT reaches power good before its EN is asserted?

    Regards

    Yihe

  • 0 in reply to yihe
    Intellectual 970 points

    UCD9090A @ PMBus Address 104d Project_0206_v3.xmlHi Yihe,

    I am not sure of the difference between using the GPO and enable. I tried using the enable for another rail (VCCINT), but I did not see the sequence complete. I have included my latest project with this enable  also.

    Regards,

    Guy

  • 0 in reply to guy lemire
    TI__Guru 66920 points
    Please provide a waveform of VCCINT rail, Pin 4, Pin 7. does it reach power_good after GPIO2(PIn 5) is high?

    What does it mean incomplete sequence?

    Please be aware that 5V rail is under operation mode while the other three are under control pin.

    Regards
    Yihe
  • 0 in reply to yihe
    Intellectual 970 points

    UCD9090A @ PMBus Address 104d Project_0207_v1.xmlHi Yihe,

    I think we are getting our wires crossed a bit :).

    For testing my lab image, I only wanted to use one pin in operation mode (enable ). I was getting confused when you mentioned setting all the supplies to operationsl mode (enable), in order to monitor the voltages with the power designer software. All the other voltages I will use GPOs with logic to control the sequencing. For normal operation in mission mode, I want to run with the enable in GPO mode. I have attached my latest project. I am able to sequence through the rails, but I am still seeing a few issues. As you can see I need to manually set the 5V enable to have the sequence proceed. Is there any issue with setting up my sequence using GPOs only?

    Regards,

    Guy

  • 0 in reply to guy lemire
    TI__Guru 66920 points

    I would recommend to read page 30 of http://www.ti.com/lit/pdf/slvub51   to understand multiple ways to turn on/off sequence for power rails.

    If you do not want to manually turn on 5V, please set it ON/Off Config to Auto(none). so that when UCD is out of reset, it will turn on 5V automatially if 3.3V is above power good.

    There is one issue with your settings

    why 3.3V rail has turn on dependencies on Rail #3(1.8V) . Is this a mistake?

    We recommend to EN function of the rail instead of Logical controlled GPO to turn on/off rail. the reasons are that EN function are part of the sequencing engine, it is directly connected with various state of the power rail internally. While having LGPO is kind of indrectly way and you may miss some fault response protection or run out of logic to do some resequencing.

    For example, when the rail has no EN pin associated with it, there is no meaning to set the turn on/off dependencies. any timeout action of the dependencies check is not going to work since there is no EN associated with the rail.

    http://www.ti.com/lit/pdf/slua815  is a also a good starting point to understand the device.

    i had modified your file to use EN function instead of LGPO to do the same function.  You do not have to manually turn on 5V rail. you can review the file under offline mode first before importing to the device.

    UCD9090A @ PMBus Address 104d Project_0207_TI.xml

    Regards

    Yihe