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Problem in ucd9222 + ucd7242 Working below -20℃

Hengwei Xiang
Intellectual 360 points
Other Parts Discussed in Thread: UCD9222, UCD7242

Hi everyone,

     I am using ucd9222+ucd7242 for c6670.Rail 1# is 0.9~1.1v,rail 2# is the fixed 1.0v.Our product run normally above -20℃,however,run abnormally below -20℃.At this moment,the PG pin of rail2# is low level.What can I check my circuit?

  • 0
    TI__Genius 9845 points
    Hi Hengwei,1. What fault does the Fusion GUI report?
    2. What is your capacitor's temperature rating?
    One possibility is that, the capacitance changed quite a bit with temperature, and the control loop became unstable. But we need to look into the GUI first.
    Thanks,Zhiyuan
  • 0 in reply to Zhiyuan Hu
    Intellectual 360 points

    Hi Hu,

         The report of GUI is following ,when the temperature is -30c.

  • 0 in reply to Hengwei Xiang
    TI__Genius 9845 points

    Hi Xiang,

    1. Which rail do you have problem with? Your screenshots show Rail#1 is -24degC, Rail#2 is 32degC. But the rest of screenshots show Rail#2 information. If you have problem with Rail #1, please provide Rail#1 screenshots.

    2. Why is there such huge temperature difference between the two rails?

    3. It seems your Vin is unstable. Have you measured Vin waveform on scope to confirm?

    Thanks!

    Zhiyuan 

  • 0 in reply to Zhiyuan Hu
    Intellectual 360 points

    Hi Hu,

    1.I have problem with Rail 2#,then I only provide Rail 2# screenshot.

    2.Yes ,I see too.That is ,does the ucd9222 have problem in Rail 2# below -20c?

    3.I have measured Vin.Vin is stable in 12V.But it is shown 10v in GUI.However ,it is stale under any temperature.

    Hengwei

  • 0 in reply to Hengwei Xiang
    TI__Genius 9845 points

    Hi Hengwei,

    UCD9222 is rated from -45degC to 125degC. So I would check the external circuit first.

    Some components on the board may not be rated for such a low temperature, such as capacitor. Also, on the PCB, solder joints may have contraction cracks, which may change the resistance or even disconnect the circuit. These are my speculations.  

    Here are some questions to help you identify the problem:

    1. When the board returns to room temperature, do the problems disappear? If the problems persist, it means the external circuit is damaged.

    2. When you measured Vin=12V but GUI reported 10V, did you measure the voltage on the pin?

    3. The temperature of Rail#2 reported in GUI is wrong. Is it correct at room temperature? Is it calibrated? When the reading is wrong, did you measure the voltage on the pin?

    4. Is it possible to physically swap the connections of  temperature sensing pins on the board? After swap, if the GUI reports Rail#1 is +30degC and Rail#2 is -30degC, it means the problem is in external circuit; if the GUI still reports Rail#2 is +30degC, it means the problem is in UCD9222.

    5. The two rails report both UV and OV. It would only possible if the output voltages swing a lot. Did you check the voltage waveform *on the sensing pins* when the faults happen? If you clear the faults in the GUI, do the faults re-occur?

    Thanks,

    Zhiyuan

     

  • 0 in reply to Hengwei Xiang
    TI__Genius 13700 points
    I think there might be something wrong in your configuration file for the UCD9222, specifically I noticed that the UCD9222 is reporting that the UCD7242 has a large negative current flowing. This is not possible as the UCD7242 cannot report negative current.
    Please forward your configuration project file (.XML) for the UCD9222 and a copy of your power system schematic.
  • 0 in reply to Brad
    Prodigy 160 points
    Hi, I met this similar issue that the 9222+7242 can not power up ok below the -0 deg C. I find the pwm freq is not the one I set in the config file(xml file set 67okhz,but from the oscillator, it show about 580khz). I also use the same xml file to config the 9222 in another different board, it is ok for the pwm freq and it can work well under the -0 deg. Any suggestion for this case? thank you!
  • 0 in reply to stonenut lin
    TI__Genius 9845 points

    Is there any fault or just frequency change?

  • 0 in reply to Zhiyuan Hu
    Prodigy 160 points

    9222 can not connect to the GUI under 0 temp, so I can not see any fault code about this case up to now.

    this issue is not only on one board. it seems all boards have this case. so it should not the IC issue. the pwm freq issue is found recently, it can not output the correct one as set in the xml file.

    I also use the same xml file to config another board(different product and 9222 have different layout, but the schematic is the same), it can work ok under the 0 temp and the pwm freq is the one set in the xml file. (BTW how can I upload the xml file here?).