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uCD9244 4-phase 1-rail supply: if possible?

Other Parts Discussed in Thread: LM10011, UCD9246, UCD9244, UCD7242, UCD9248, UCD9224

Hi All,

I need to design 4-phase VID-compatible power supply for CPU VCore.

I thought to use uCD9244. Another alternative, which seems to be valid is to use uCD9246/8 and LM10011 in feedback for VID.

As far as  I see from documentation, reference TI designs and Fusion Digital Power Designer, uCD9244 does not support poly-phase configuration. However, there is at least one design (Advantech K2H_K2EVM), where uCD9244 used with 2 rails working together.

What is the special uCD9244 configuration, which should be applied in this case?

Is it possible to perform current balance and phase shedding with uCD9244?

Is there any future device planned with VID and poly-phase configuration support?

One more question: I've got strange message from Fusion Digital Power Designer:

"Rail #1: To insure monotonic start-up into prebias, DRIVER_MIN_PULSE (20.000 ns) must be larger than 1/64th
of the switching period (FREQUENCY_SWITCH = 500.000 kHz).
Either increase the DRIVER_MIN_PULSE (to greater than 33.250 ns) or
increase the FREQUENCY_SWITCH (to greater than 868.056 kHz)"

This happens when I tried to configure uCD9244 with uCD7242 (DRIVER_MIN_PULSE=20ns) for more than 500kHz operation. The GUI simply does not allow me to change frequency. Both uCD9244 and uCD7242 are listed as capable of up to 2MHz switching, but here there is additional limitation. Can this somehow be changed?

Thanks in advance for answers!

  • The UCD92xx VID controllers only support single phase rails and there are no UCD92xx devices presently in development which will support VID and multiphase.  I beleive the EVM you reference drives two phases in parallel and would not benefit from spreading the phases out equally during the switching period, even more beneficial for 4 phase designs.

    I have not used the LM10011, but from taking a quick look at the datasheet it appears that it could be used with a UCD9224 (which can support a single rail with 4 phases) or the UCD9246/UCD9248 to produce a 4-phase rail with VID support.

    Alternately, depending on your voltage update rate, if you have the capability of writing the PBus command VOUT_COMMAND to the controller then you could adjust the voltage this way rather than with VID pins and would not need the LM10011.

    There shouldn't be any issues with changing the frequency, unless the rail is operating while attempting to change the frequency which is not allowed.  You can also change the DRIVER_MIN_PULSE on the Configure page under the Advanced Config tab.  The GUI defaults to 20ns for the UCD7242 driver.

    If the Advanced Config tab is not visible, go to the File dropdown and select the Preferences, check the "Show advanced editors and features...." checkbox and click OK.