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UCD9222: Something wrong when I use UCD9222 and UCD7242

Part Number: UCD9222
Other Parts Discussed in Thread: UCD7242

Dear engineer of TI, I am in the process of debugging the UCD9222 and UCD7242 power module. I used the Fusion Digital Power Designer v7.0.11 and use the Firmware&Configuration Download Tool to download project file, run the GUI ONLINE mode, the monitor interface shows that the input voltage and temperature, but there is no output voltage and output current, the Status Registers show a yellow warning" output off" and "powergood#", other items show OK. But when I pull up the Control Line, the GUI shows that the adapter has been disconnect with device, and then the device was reset, and disconnect again, reset again, repeat it several times. I can't stop it until I pull down the Control Line. What wrong with it?

  • I think the reset pin of UCD9222 was pulled low by the external circuit. Please check reset pin waveform.

    Also, check if 3.3V supply is stable.

  • Thank you, Zhiyuan Hu. I try to configure only one voltage rail(CVDD) to C6678, when I pull up the control line, the voltage rail works well. But when I configue two voltage rail(CVDD&DVDD) as what I did before, the CVDD is good, the DVDD showed TON MAX FAULT and POWERGOOD#, there is no output on DVDD. The DVDD is a fixed 1.0V voltage rail, and it has a 5ms turn on delay compare to CVDD. What is the reason?
  • TON MAX fault means the rail was not able to ramp up to target voltage within the configured TON MAX time period. It is possible that your configured TON MAX time is too short; increasing it will solve the problem. Or maybe there is problem with the rail so the output voltage cannot ramp up; you will need to measure operation waveform to find out what happened.
  • Hi,Zhiyuan Hu. I found the SWITCH FREQUENCY can influence the stabilization of the power. When I write the SWITCH FREQUENCY as 799kHz, the GUI show that device was reset immediately. When I write 449kHz, I can configure only one voltage rail(CVDD) to C6678, drive another rail will cause the device reset, just like the phenomenon as before. I also tried the 249kHz, the two voltage rail(CVDD&DVDD) can be driven at the beginning, but when I run the code about PLL configuration, the GUI show that device was reset again. When I write 229kHz, the power was stable and never reset itself. I don't why the TI's 6678 EVM board use 799kHz SWITCH FREQUENCY, but my board only can use 229kHz? What happened when I reduce the SWITCH FREQUENCY?
  • I think the inductor or capacitor value in your design are different from EVM or has changed. Otherwise the same compensator configuration should work.

    It is expected to see loop stability change with switching frequency. With the same parameters in a digital compensator, the zero-pole frequencies will change with switching frequency. The switching frequency information is used when converting from z-domain to s-domain. So, after changing switching frequency, you need to also update compensator value to make zero-pole frequencies unchanged.