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UCD9244 Output Paralleling

Jonathan Salles
Prodigy 180 points
Other Parts Discussed in Thread: UCD9244, 66AK2H12, UCD7242

In the Rev 3.0 of the Advantech XEVMK2HZ evaluation module there is a UCD9244 controlling two UCD74120s.  The outputs of both are tied together after the inductors to generate a single CVDD supply for the Keystone II.  The PWM inputs can also be tied together, though it is not clear that this is done because of the use of zero ohm resistors.

I am having trouble trying to set up the UCD9244 to accomplish this.  Advantech does not provide the project files for this evm, though they do provide them for other evms.  Can anyone tell me how one would go about driving two differently configured UCD74120s (different inductors, power output, etc) with one controller in a UCD9244 that will generate one voltage?

  • 0
    TI__Genius 13700 points

    What is the reasoning behind two different power trains in parallel?

    Can you provide a schematic or block diagram of what you are trying to acheive?

  • 0 in reply to Brad
    Prodigy 180 points

    Paralleling two power trains is what Advantech seems to have done in their latest eval board for the KeystoneII.  We are designing a board with the 66AK2H12 which now has the previously separte ARM and DSP vCORE shorted together.  I am trying to determine if I should follow the Advantech reference design or just use a single train to power both cores.

    The reference design seems to be driving two trains or PWM circuits with one controller section.  The outputs are shorted together to increase the power.

    K2H_K2EVM-HK_SCH_A104_Rev3_0_pg40.pdf
  • 0 in reply to Jonathan Salles
    TI__Genius 13700 points

    I remember this design now. As I recall, the DSP group was unsure if they planned to run seperate supplies for each core and they designed the board so that they could go in either direction if needed.  Although both outputs are labeled the same, they had the capability to seperate them.

    You will need to check the DSP documentation or contact the DSP group for their recommendation on combining these rails or not.  At the time they were planning to use just the 20A powertrain if both cores were to be powered from the same rail.

    Note: If you plan to combine the cores on the first rail and use the two fixed core supplies on the UCD7242 then it would be best to move these two powertrains from rails 3 and 4 to rails 2 and 3 otherwise you will need to create a dummy rail on rail 2 because it cannot be skipped in the configuration file.