LDO Input Voltage Fluctuation

[tiwari.sachin]

How would the output of LDO (1117-3.3V) effect/change if the input voltage fluctuates. Will the output be stable enough?


I am using a input voltage of 9V (This can fluctuate a lot as I am connecting it to a thermal printer power which causes this fluctuation during printing only due to variable current consumption and happens for few 100 ms)

 

[betwixt]

For very rapid changes in input (step changes) look at the transient response in the data sheet. For more gradual changes you shouldn't see any significant change in output as long as the input stays above the drop-out threshold.

Brian.

 

[tiwari.sachin]

For very rapid changes in input (step changes) look at the transient response in the data sheet. For more gradual changes you shouldn't see any significant change in output as long as the input stays above the drop-out threshold. Brian.

Transient response will tell me the ability of ldo to hold its output voltage when theres change in load current connected to that output.

My concern is the input to the ldo... because this input drives another load which can cause drop or variations in the input voltage that is given to the ldo. This input voltage is from a battery or a dc adaptor

 

[danadakk]

Page 11 shows transient response -

https://www.ti.com/lit/ds/symlink/lm1117.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&ts=1600981991065

Note that is influenced by other bulk C on the rails in the design.


Regards, Dana.

 

[barry]

Transient response will tell me the ability of ldo to hold its output voltage when theres change in load current connected to that output.

There is load transient response AND input(line) transient response. Look at just about any data sheet