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We are trying to design a power supply that runs from two AAA batteries wired in parallel and outputs 3.3V. The requirement is to keep the peak to peak ripple voltage under 10millivots. For our design we are using 2 stages. 1 to boost the voltage of the cells and one to regulate the voltage. The regulator we chose is the NCP702.
We are using a boost converter for the first stage. This boosts the voltage from 1.5V to 5V. Our first stage booster produces an output ripple of about 60millivolts.
The second stage is the NCP702 LDO.
From the device we obtain a ripple voltage of about 14millivolts.
Even running the regulator directly from a 4Volt cell we obtain a ripple of about 8mv to 10mv peak to peak.
The data sheet states that we can get a ripple of 11microvolts RMS. The peak to peak of a rms value of 11microvolts assuming a sine wave is still one order of magnitude lower then what we are obtaining.
What recommendations are there to reduce ripple from this device? Any Advice or recommendations would be greatly appreciated.
We need more information – schematics (at least the one of the second stage with LOD) with values and types of the capacitors, scope pictures of the NCP702 Low Dropout Regulator input and output voltage, load information and details about their test set-up. We cannot correctly answer without this. Please contact us directly via technical support.
Answered by: ON Semiconductor
2013-04-10 15:05:31.796