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TPS74401 Vbias

Jesus Martinez81
Prodigy 50 points
Other Parts Discussed in Thread: TPS74401, TPS7A7001

Hello,

I would like to use the TPS74401. The input voltage will be 2.5V and the output 2.2V with Iout(max)=2A. I want to know if I can tie Vbias with Vin becuase I only have one voltage source.

Reading the datasheet (8.2.4. Without an Auxiliary Bias) I make my figures

Vin < Vout + 1.62V 

2.5 < 2.2 + 1.62V then I need an auxiliary voltage source for Vbias

Are these figures ok? Can I tie Vbias with Vin?

Thank You

Jesus

  • 0
    TI__Guru 55940 points
    Hi Jesus,

    Vin and Vbias may be tied together; however, in order for the LDO to regulate, the Vbias dropout spec must be met. In your case, in order for regulation, Vin and Vbias should be 3.82V if tied to the same voltage source.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 50 points

    Because I've only one voltage source I should change the voltage regulator, TPS74401 won't suit my design.

    I´ve measured which is the maximum current that I need and it's below 1.5A.

    With Vin=2.5V and Vout = 2.2V, very close I think TPS7A7001 could be the option 

    In order to guarantee the regulation (normal operation) as follows from datasheet: 

    Vin > Vout(nom) + VDO

    For Iout=1.5A the datasheet gives VDO=300 mV that means that if I reach this Io=1.5A the regulator will change to dropout operation and no regulation will occur.

    Am I right? Do I have a better choice with less risk?

    Jesus

     

     

  • 0 in reply to Jesus Martinez81
    TI__Guru 55940 points
    Hi Jesus,

    You are correct that TPS7A7001 looks to be more suitable for your application. You have adequate headroom with 300mV to keep TPS7A7001 out of dropout.

    Very Respectfully,
    Ryan