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TLV772: PTLV77201PDBVR

Linda Lee
Prodigy 10 points
Part Number: TLV772

Tool/software:

Hi teams,

I want to use the TLV772. But I don't know how to calculate the R1 and R2.

I need your help to provide solutions for R1 and R2.

1. Vin=5V, Vout=2.2V, R1/R2 ≈ 2.6667 and R1+R2< 330K ohm

2. Vin=5V, Vout=3.3V, R1/R2 = 4.5 and R1+R2< 330K ohm

Thanks.

BR, Linda

  • 0
    TI__Genius 12550 points

    Hi Linda,

    Using 1% resistor values, these are the closest options:

        1. R1 = 20kΩ, R2 = 7.5kΩ, Vout = 2.2V

        2. R1 = 11.5kΩ, R2 = 2.55kΩ, Vout = 3.306V (0.2% above 3.3V setpoint)

    I suggest using a divider calculator like this one:  Voltage divider calculator for real E-series resistors.

    Another method is to rewrite R1+R2 = Rtotal as R1 = Rtotal - R2 and substitute into the first equation. R1/R2 = Ratio can then be rewritten as R2 = Rtotal/(Ratio + 1).

    This will allow you to solve for one of the resistances as a function of the total resistance. You can then adjust the total resistance to find an R2 value that's a standard value (refer to a list of E-series values like E series of preferred numbers - Wikipedia) and then select an appropriate R1 value to get as close to your required ratio as possible. This may require a few iterations to get the closest possible match, however. 

    Best Regards,

    Alex Davis