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Fusion Designer Schematic Entry for UCD9244

Jonathan Salles
Prodigy 180 points
Other Parts Discussed in Thread: 66AK2H12, UCD74120, UCD9244, UCD9222

My design for a project with a 66AK2H12 has copied the power circuitry from the  K2H EVM from Advantech.  I was succesful in using project files created from reading the power controllers and creating new project files and using those to get the board running.  The design uses a UCD9244 PWM Controller and UCD74120 Buck Power Stage.

Reading the power controllers and creating the project files only gets the parameters that were created, and does not produce the design schematic.  When I enter the schematic and attempt to enter the components, I find that the schematic in the Fusion Designer differs slightly from the schematic on the K2H EVM.  The differences are:
1) On the reference design SRE is separate and pulled up to 3P3V with a 10K.  In Fusion Designer SRE is tied to SRE_MD and BP3.
2) In the reference design IMON goes through a 100 ohm to connect to CS inputs and a 4.99K is in parallel with a 10nF cap at the CS input.  In fusion designer IMON goes through a 4.99K to get to the CS inputs and a 10nF connects the CS input to ground.

These differences look like they would affect the way the circuit operates, especially the current monitoring.  These differences are not changeable in the Fusion Designer.  How can I account for these differences when I try to create a project file with the components?

Thanks,

Jonathan Salles
CSPI

  • 0
    Prodigy 180 points

    Will anyone from TI answer this?

  • 0
    TI__Genius 13700 points

    1)  The application diagram in the driver datasheet is consistent with a non-VID UCD92xx controller application, in this case the SRE signal would be available from the controller and the SRE_MD pin is tied to BP3.  With the VID enabled UCD9222 and UCD9244 there is no SRE signal coming from the controller.  When using a VID-enabled controller, it is necessary to tie both the SRE and the SRE_MD pins to 3.3V.

    The DSP EVM ties SRE_MD to the driver's BP3 pin (local 3V3 source) but ties SRE to the 3V3 supplying the UCD controller.  I prefer to use the driver's BP3 signal to terminate both SRE and SRE_MD.  This saves having to run the controller's 3V3 to the driver.  Either option will work, no pull-up is required.

    2)  Apparently, the DSP EVM designer's felt the IMON signal needed some additional filtering, the 100ohm resistor isn't required.  If it is used then the IOUT_CAL_GAIN and IOUT_CAL_OFFSET values need to be adjusted manually for the difference but the resistor divider of 100 ohms over 4.99Kohms is only ~2% difference.

    Replacing the 100 ohm with 0 ohm and you can use the values generated by the Fusion GUI.

    .

     

  • 0 in reply to Brad
    Prodigy 180 points

    Thanks for the answers Brad.  

    To program my UCD devices I used project files I pulled out of the UCD devices on the XCTIEVM2KX eval board.  Interestingly the VID option is off in these files, but the device is connected for VID.  Am I correct in thinking the connections for the VID have no effect on the calculations of the Fusion Designer?

  • 0 in reply to Jonathan Salles
    TI__Genius 13700 points

    Yes, that would be correct, if the VID option is not enabled.