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LDO voltage output on supplying voltage below 3V

shantanu nakhate
Prodigy 30 points

Hi All,

I have a basic question with regard to functioning of TLV71730P LDO. 

This is a 3V fixed output LDO functioning from 1.7V to 5.5V max.

By above is correct to say that:

The LDO shall output 3V when the input is greater or equal to 3V and

when input voltage is less than 3V, is it correct to say that Output Voltage shall be equal to input voltage?

E.g.

Output Voltage = 3V for Input voltage  = 4V

Output Voltage = 2.5V for input voltage = 2.5V

Thanks and Best Regards,

Shantanu,

  • 0
    TI__Expert 3735 points

    Hey Shantanu,

    Not quite. The situation you are describing is contingent upon the device's dropout specifications. At full load (150mA), the dropout of TLV71330 is 445mV maximum, as the table indicates below:

    This implies that in order to properly regulate 3.0V, the input must be 445mV higher, or 3.445V. If the input should drop below this value, there's a chance that the output can also droop. If we were to consider the input dropping to 2.5V, the output will maintain the dropout delta and become 2.5V - 445mV = 2.055V.  

    However, at no load (0mA), the dropout shrinks significantly. It's likely that if the input is 2.5V, the output will either be 2.5V or very close, like you stated before.

    Hope this helps,

    Aaron