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KEYSTONE II Power Sequencing Problem

Ayhan Gunesdogdu
Prodigy 30 points
Other Parts Discussed in Thread: UCD9090, UCD9244

Hi,

 

We have designed own Keystone II  card based on EVMK2H structure. We used same chips.

 

There is a power sequencing issue due to UCD9090, and UCD9244s . In some cases, VCCA0V75, VCCB0V75, VDD33 couldn't start.

 

I have checked power chips via Fusion Digital Power Designer  programming adapter, but I couldn't find reason of failure.

 

When I re-programmed UCD9090 and UCD9244s with EVMK2H's projects, all power chips runs properly. After a few on/off operation, VCCA0V75, VCCB0V75, VDD33 couldn't start again.

 

Is there any way to find reason of power sequencing failure ?

 

  • 0
    TI__Mastermind 42545 points

    Hi Ayhan,

    Let's separate the power sequencing from the power supply start-up issue. The UCD9090 provides enable signals which are used to turn on each power supply in the sequence. The first thing to check is the enable signals. Are the enable signal present and are they transitioning at the proper time and at the proper voltage? If the enable signals are present then this isn't a sequencing issue, it's a power supply start-up issue. There are many reasons that a power supply may fail to start. It is best to address these questions to the forum which supports the specific power supply that you've designed into your system. You have indicated that you are using the UCD9244 but are having problems with the VCCA0V75, VCCB0V57 and VDD33 supplies. Are you using the UCD9244 to generate these voltages? Generally, the 0.75V are generated using a DDR VTT termination supply and the VDD33 doesn't require much current. The UCD9244 is used to control the higher current supply rails on the EVM and are not used for these voltages. 

    Regards, 

    Bill