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TPS74901 : VBIAS connection

Chirag Rasputla
Prodigy 190 points
Other Parts Discussed in Thread: TPS74901


Hello,

    Have freezed TPS74901 regulator for PS design to regulate input 5V to output 3.3V , want to finalize the design but have confusion over VBIAS connections as datasheet mentions the following:

1) If VIN and VBIAS are connected to the same supply,  the recommended minimum value capacitor for VBIAS is 4.7uF.

2) While figure 26 mentions VBIAS connection with auxiliary supply with better efficiency as compared to figure 27.

Please suggest with what option would be better for VBIAS pin.

Thanks & Regards,

Chirag 

  • 0
    TI__Guru 55940 points
    Hi Chirag,

    You are correct that when Vin and Vbias are connected to the same supply, the recommended minimum capacitor is 4.7uF.

    The reason for the higher efficiency when connected to separate rails is due to the lower dissipation from Vin to Vout. When connected to separate rails, you can reduce the input voltage and therefore create a more efficient system.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 190 points

    Hello Ryan,

             Thanks for the suggestion, will proceed the design by connecting Vin and Vbias together with recommended minimum capacitor of 4.7uF for Vbias.

    Regards,

    Chirag