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About LP2951-50 accuracy at 50mA

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: LP2951

I have  a aquestion.

My customer will use LP2951-50 under thefollowing conditions.

Input Voltage : 24V

Output Voltage : 5V

Output Current : 50mA(max)

I checked the datasheet P.5 about output voltage.

Max : 5.1V(IL=100µA)

typ : 5.0V(IL=100µA)

output accuracy : 2%

and I checked  the dataseet P.6 about Reference Voltage.

  Max : 1.272V(-40℃~125℃,Vout=Vref to(Vin-1V),Vin=2.3V to 30V,  Ilim=100µA to 100mA)

  typ : 1.235V(25℃)

 Output accuracy=2.99%

Is the output voltage accuracy of LP2951  below 2% when customer's condition(50mA)?

best regards

  • 0
    TI__Mastermind 24975 points
    Hello Nishizawa-san,

    I apologize for the delay in response.
    When considering the fixed output voltage option, the reference voltage variation is considered as part of the output voltage min and max.
    To be clear, what I am saying is that the 4.9V and 5.1V are the minimum and maximum output voltage due to variations from the reference as well as process variation (which also includes the internal resistors).
    So a given device could have a voltage in that range over temperature when 100uA load is present.

    That spec is important, but the other spec you want to look at is the load regulation. The maximum load regulation over full temperature range is 0.3%. So that could add up to a 0.3% variation as well.

    Also considering the loading conditions there could be variation due to change in temperature. With a 19V drop and 50 ma, thats approximately 1W of power which could change the output voltage in worse case by 0.2%

    When you add all of these up, it could be as bad as 2.5%, but in actuality not all changes are going to affect the output in the same direction, and these are absolute worst case conditions that are guard banded to ensure that they are not exceeded.

    The 2% variation to begin with is very high and when you consider the other specifications, they are also not likely to reach their maximum variations.

    Therefore I would expect extremely few, if any, devices to not fit within 2% accuracy under those conditions.

    Best,
    Michael