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TPS717-Q1: Output Voltage calculation

Sudharshan J
Prodigy 20 points
Part Number: TPS717-Q1

Hello TI technical team,

The below snap presents the Query related to the TPS71701QDRVRQ1 LDO

 

 

Please find TI response

 

 

 My query regarding the above response is 

  1. Cant we include Feedback pin leakage current in calculating the output voltage, as below 

 2. As mentioned in response, if 1uA is the amount of current that can flow into the pin before the pin is damaged, please confirm the maximum Feedback pin leakage current need to be considered.

 

Thanks and regards

Sudharshan 

  • 0
    TI__Expert 3870 points

    Hi Sudharshan,

    1. Yes you can include IFB in the output voltage calculation as you are showing it. 

    2. The maximum feedback pin leakage current (that doesn't damage the LDO) is directly related to the output accuracy of +/-3%. If you rearrange your formula for Vout = 5V +/-0.15V and solve for the feedback pin leakage current you will be able to find a good estimate. 

    I did the calculation for Vout = 5.15V and in this case IFB = ~0.1uA

    However, I believe you may get a better analysis if you consider both the output accuracy of +/-3% and the change of Vout due to the load. For example, if your load were 100mA at 85ºC, your change of Vout would be -12mV. Then for +3% accuracy you get Vout = 5.138V and for -3% accuracy you get Vout = 4.838V. 

    Regards,

    Andres