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UCC2895: unstable factor

Hyeonseung Ju
Prodigy 40 points
Part Number: UCC2895

hi i'm looking for a information about ucc2895DW or ucc2895q (automotive)

if Ramp connect CT with Low Risistance (ex 2.2R) , does it damage to Inside circuit?

i'm worried about that circuit..

the circuit that i connected Ramp and CT witch low resistance looks like operating well

  • 0
    TI__Guru* 83236 points

    Hello,

    I believe that puts the UC2895 to operate in voltage mode control.  So  you will need a DC block capacitor in front of the HBRidge to prevent transformer saturation.  

    Most designers choose to use peak current mode control to avoid using the DC blocking capacitor.

    The CT ramp peak is 2.55 V max and the min is 0V according to the data sheet.  The Ramp pin is rated for -0.3V to REF +0.3 V.  So you are not exceeding the rating of the UCC2895.  However, if your transformer saturates the UCC2895 may not be fast enough to cycle by cycle current limit the HBridge.

     

    Regards,