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TPS54325: Minimum Input to Output voltage difference for TPS54325 and TPS54425

Hung Ching Hsu
Expert 3086 points
Part Number: TPS54325
Other Parts Discussed in Thread: TPS54425,

Hi Team,

My customer wants to know the minimum Input to Output voltage difference for TPS54325 and TPS54425, could you kindly help? 

Or should customer better input the condition they want to Webench and confirm?

Thanks.

Regards,

Jo

  • +1
    TI__Guru 50135 points

     

    The maximum Vout to Vin ratio that a converter can support can be limited by a number of factors limiting the maximum duty cycle and output voltage.

    For the TPS54425 and TPS54325 the maximum duty cycle is limited by the 700kHz switching frequency and the minimum off-time.

    At 700kHz the 310ns minimum off-time limits the duty cycle to 78%, so VOUT can not be more than 78% of VIN.  This maximum output voltage is further reduced by the efficiency and losses in the power stage and inductor. With a low conversion ratio those losses will be dominated by the I-R loses of the high-side FET and inductor DCR.

    In addition to the duty cycle limitations, VOUT is limited to 5.5V by its D-CAP2 internal ramp generator which can saturate and compromise the control loop stability if the average switching node voltage exceeds 5.5V.