Question about regulator.

[hanm]

Hi all,
I have a problem about regulator: I transform a 3v power supply to 2.5v
for inner digital circuits use, when the digital circuits work, glitch will arise
because transition inside it,then the 2.5v supply line will drop to 2.3v at the
transition point sometime and rise to 2.63v else, all the time the signal
output is right.

My question is the 2.5v supply drops and rises to this degree is reasonable?
Is there any dangerous?
Thank you.

 

[IanP]

Without knowing details of your circuit I would say voltage should not drop or rise by more than ≈5%.
In this case it is close to 10% ..
Try to "silence" the path between voltage regulator and circuit by implementing L-C low-pass filter ..
Regards,
IanP

 

[sunking]

you can run you digital circuit under this voltage(2.3 and 2.53) to verify the function.
in fact, as IanP said, +-10% supply error is OK for a good digital circuit design

 

[hanm]

Ok. I see.Thank you, IanP and sunking.

 

[surianova]

Hi all,
I have a problem about regulator: I transform a 3v power supply to 2.5v
for inner digital circuits use, when the digital circuits work, glitch will arise
because transition inside it,then the 2.5v supply line will drop to 2.3v at the
transition point sometime and rise to 2.63v else, all the time the signal
output is right.

My question is the 2.5v supply drops and rises to this degree is reasonable?
Is there any dangerous?
Thank you.

You can reduce the ripple by reduce the output impedance of the voltage regulator or increase the gain of error amplifier.

 

[VVV]

10% drop sounds like a lot to me.
The real question you need to answer is why this is hapening. Is it because the regulator does not have enough headroom (should be an LDO, for only 0.5V I-O differential), or is this poor transient response, or is the 3V dropping so low that the regulator runs out of headroom? Or perhaps the load current is too high?

To do that, test the regulator at constant output current (just a resistive load), and check its output voltage.
Then check its headroom: reduce the 3V until the output voltage begins to drop and see how much it needs to maintain 2.5V.
Then check what it takes (increase load current) to drop the output to 2.5V.
If all the above tests indicate the regulator should work properly, then check the transient response.

 

[johnyaya]

Is the regulator meeting it's specs? Which regulator are you using?

 

[disney]

Looks like there is leakage current....
Try to find what is your quiscenet current.