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UCC28064A: Mode and freqency of UCC28064A

Takahara Motoki
Prodigy 110 points
Part Number: UCC28064A

Tool/software:

Hi, TI

I have two questions.
Please give me an advice.

1
As shown below, there are cases where it operates in single mode and interleaved mode depending on the input conditions. Is this normal?
I'm particularly curious as to whether single mode at 85W DC input is normal.
Case A：AC85V、170W　interleaved mode
　　　 　AC85V、85W　interleaved mode
Case B：AC220V、170W　interleaved mode
　　　 　AC220V、85W　interleaved mode
Case C：DC93V、170W　interleaved mode
　　　 　DC93V、85W　single mode
Case D：DC144V、170W　interleaved mode
　　　 　DC144V、85W　single mode
(RU_PHB=220kohm、RD_PHB=68kohm)

2
Is there a maximum frequency?
I have cases where it operates at 103kHz, and I would like to confirm whether this is normal?

Best regards,

  • 0
    TI__Mastermind 40260 points

    Hello Takahara-san, 

    1.  Whether AC input or DC input, the UCC28064A has voltage feedforward (at the VINAC input) which keeps the voltage-loop gain constant over input voltage range. 
    There for the COMP voltage is proportional to load.  

    The light-load phase-shed function (at PHB pin) appears to be set for ~85W as the COMP voltage falls, and resume 2-phase operation at ~175W as COMP voltage rises. 
    This behavior is normal.  The actual thresholds are set by the user. 

    2.  There is a maximum frequency based on a minimum-period timer whose time is proportional to Rtset.  This could be up near 400~500kHz, but usually other operating factors prevent the system from reaching this high.  
    In any case, 103kHz is normal.  

    Regards,
    Ulrich