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Search for a scope to measure LDO regulator noise and PSRR
Search for a scope to measure LDO regulator noise and PSRR
Hi guys,
I am searching for a scope hopefully using it to measure noise and PSRR of a LDO regulator. The simulation results for noise is shown in the attached graph.
For PSRR measurement up to 20MHz, I suppose 5000series scope has function generator up to 20MHz in addition to the scope main functions and therefore can serve such purpose.
Please can you advise me on the noise measurement side? Does the software has Spectral noise density analysis function? Has anyone used PicoScope for noise measurement before?
Thank you and I look forward to your reply
Cheers,
John
I am searching for a scope hopefully using it to measure noise and PSRR of a LDO regulator. The simulation results for noise is shown in the attached graph.
For PSRR measurement up to 20MHz, I suppose 5000series scope has function generator up to 20MHz in addition to the scope main functions and therefore can serve such purpose.
Please can you advise me on the noise measurement side? Does the software has Spectral noise density analysis function? Has anyone used PicoScope for noise measurement before?
Thank you and I look forward to your reply
Cheers,
John
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Re: Search for a scope to measure LDO regulator noise and PSRR
Hi John,
I apologise for the delay in answering (this post got overlooked in the run up to Christmas).
If you are still investigating the PS5000 series for noise and spectral noise density measurements, the I would have to inform you that this would not be a suitable application for this PicoScope series, or for our PicoScope 6 software.
The 5000 series PicoScopes have a relatively large input noise (in comparison to a lot of our other PicoScopes) and for making the measurements in spectrum Mode you would not be able to utilise any of our software methods of noise reduction. Also Our PicoScope 6 software only plots an Amplitude Spectrum of V/Hz and converting to a power spectrum of V^2/Hz (or V/√Hz) is overly complex. You could overcome the Spectrum issue by using our Software development Kit to build an application that will acquire the data in Matlab, and then use their ready made library with a Power Spectrum.
However, if your requirement is not immediate, then we have new technology on the way which is likely to satisfy your requirement.
Regards,
Gerry
I apologise for the delay in answering (this post got overlooked in the run up to Christmas).
If you are still investigating the PS5000 series for noise and spectral noise density measurements, the I would have to inform you that this would not be a suitable application for this PicoScope series, or for our PicoScope 6 software.
The 5000 series PicoScopes have a relatively large input noise (in comparison to a lot of our other PicoScopes) and for making the measurements in spectrum Mode you would not be able to utilise any of our software methods of noise reduction. Also Our PicoScope 6 software only plots an Amplitude Spectrum of V/Hz and converting to a power spectrum of V^2/Hz (or V/√Hz) is overly complex. You could overcome the Spectrum issue by using our Software development Kit to build an application that will acquire the data in Matlab, and then use their ready made library with a Power Spectrum.
However, if your requirement is not immediate, then we have new technology on the way which is likely to satisfy your requirement.
Regards,
Gerry
Gerry
Technical Specialist
Technical Specialist
Re: Search for a scope to measure LDO regulator noise and PSRR
Hello,
I am using a PicoScope 5444A to measure noise of voltage references together with 2 different low noise pre amplifiers.
One is a self made 1/f noise amplifier with 10000 fold amplification and limited band width of 0.1 to 10 Hz.
Schematic (attached Filt1105w.pdf) see here:
http://www.eevblog.com/forum/metrology/ ... #msg834013
PCB created by another forum member:
https://www.eevblog.com/forum/metrology ... msg1230192
The 2nd is a wide band low noise amplifier according to Linear Technology AN83 (1000 fold amplification within 10 Hz to 100 kHz).
Of course I do not get the noise density as display but only the peak to peak noise values or the FFT spectrum.
with best regards
Andreas
I am using a PicoScope 5444A to measure noise of voltage references together with 2 different low noise pre amplifiers.
One is a self made 1/f noise amplifier with 10000 fold amplification and limited band width of 0.1 to 10 Hz.
Schematic (attached Filt1105w.pdf) see here:
http://www.eevblog.com/forum/metrology/ ... #msg834013
PCB created by another forum member:
https://www.eevblog.com/forum/metrology ... msg1230192
The 2nd is a wide band low noise amplifier according to Linear Technology AN83 (1000 fold amplification within 10 Hz to 100 kHz).
Of course I do not get the noise density as display but only the peak to peak noise values or the FFT spectrum.
Andreas
Re: Search for a scope to measure LDO regulator noise and PSRR
Hi Andreas,
Those are certainly 2 ways of overcoming the level of input noise in the 5000 series, i.e. amplifying the noise to measure it above that of the PicoScope input stage noise (if you have an accurate enough noise amplifier), then apply a corresponding correction using a custom probe, and/or bandwidth limiting the signal using channel filters (if you are not interested in the rejected frequencies).
Thanks for the link to the amplifier, which may well help some users to get better use out of their PicoScopes (do you also have specs for amp?).
Note that a PicoScope 4262 would be a better option, than a 5000 series PicoScope if you'e only working with low frequencies such as in your first example (as it has a much better noise performance). You may also find that, for wider bandwidth signals, our 4000A series PicoScopes may be a better option as they have both better noise and distortion performace than the 5000 series PicoScopes (which may be better if acuracy is more important than resolution).
Also, you can get around the limitation of the missing Power Spectrum by using our Software Development Kit to create your application, using the available FFT function for plotting a power spectrum in, for example, the Matlab library.
Regards,
Gerry
Those are certainly 2 ways of overcoming the level of input noise in the 5000 series, i.e. amplifying the noise to measure it above that of the PicoScope input stage noise (if you have an accurate enough noise amplifier), then apply a corresponding correction using a custom probe, and/or bandwidth limiting the signal using channel filters (if you are not interested in the rejected frequencies).
Thanks for the link to the amplifier, which may well help some users to get better use out of their PicoScopes (do you also have specs for amp?).
Note that a PicoScope 4262 would be a better option, than a 5000 series PicoScope if you'e only working with low frequencies such as in your first example (as it has a much better noise performance). You may also find that, for wider bandwidth signals, our 4000A series PicoScopes may be a better option as they have both better noise and distortion performace than the 5000 series PicoScopes (which may be better if acuracy is more important than resolution).
Also, you can get around the limitation of the missing Power Spectrum by using our Software Development Kit to create your application, using the available FFT function for plotting a power spectrum in, for example, the Matlab library.
Regards,
Gerry
Gerry
Technical Specialist
Technical Specialist
Re: Search for a scope to measure LDO regulator noise and PSRR
Hello Gerry,
the only missing specs above are the noise floor and the passband curve.
for the 1/f amplifier the noise floor is about 100-200nVpp. But this is only valid if you have selected the input capacitor for low leakage current. (~30 nA max for the 3300 uF).
The pass band determined with the FRA4PS app of Aaron Hexamer and a 66.9 dB voltage divider is measured here. (you have to add the 66.9 dB to the measured curve to get the final result).
The PicoScope 5444A that I use is "good enough" especially when I activate a 1 kHz additional software low pass filter in the channel settings. The noise floor itself is more a function of input impedance (1000 Ohms) of the low noise amplifier. This cannot be further reduced without large influence on the noise source which often has a impedance of several 10 Ohms.
The wideband noise amplifier of AN83 is described here:
https://www.analog.com/media/en/technic ... /an83f.pdf
The cirquit contains only one bug regarding the resistor on Pin 2 of the LTC1562. The correct value would be 5K19 instead of the 5K62 in the cirquit diagram to get 0.5 dB improvement of flatness in the pass band.
This can also be simulated by LTSPICE software.
At the moment I use the amplifiers only for comparison and selecting voltage references with low noise.
So I have no need to export the values to matlab.
with best regards
Andreas
the only missing specs above are the noise floor and the passband curve.
for the 1/f amplifier the noise floor is about 100-200nVpp. But this is only valid if you have selected the input capacitor for low leakage current. (~30 nA max for the 3300 uF).
The wideband noise amplifier of AN83 is described here:
https://www.analog.com/media/en/technic ... /an83f.pdf
The cirquit contains only one bug regarding the resistor on Pin 2 of the LTC1562. The correct value would be 5K19 instead of the 5K62 in the cirquit diagram to get 0.5 dB improvement of flatness in the pass band.
So I have no need to export the values to matlab.
with best regards
Andreas
Re: Search for a scope to measure LDO regulator noise and PSRR
Thanks Andreas.
Gerry
Technical Specialist
Technical Specialist