16-bit ADC testing equipment - Page 1
Forum section: electronics / testgear

author: iheb
author_rank: Newbie
timestamp: May 02, 2023, 01:40:40 pm
content: Hello EEVersI am currently testing a 16 bit ADC, i wanted to know what is the best budget friendly approach to test this ADC and since that i am currently suffering to find a decent input source. if someone did characterize ADCs before can please help ?i have tried a lower resolution AFG but the IEEE suggests that i need something that exceeds the characteristics of the DUT for fable results.thank you for your help

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 02, 2023, 02:32:55 pm
content: If you have access to an SMU or a calibrator it’s fairly easy to write SCPI to go through the entire input range and calculate gain and offset error and integral nonlinearity. If you do not have a programmable source you can build one with a DAC, even a 10 bit one suffice, and measure the data points with a SCPI capable multimeter.Another, perhaps the first step on the plan is a zero/or mid FS measurement, to record a histogram of zero reads. It would give you a picture of noise, either from external sources, like reference or power, or internal quantization, etc. of your device. You’d like to get this close to the data sheet specs, to make sure your test setup is acceptable.If it’s a fast ADC you can characterize linearity, missing codes, etc. by taking a histogram of a low distortion sine wave.

author: Frex
author_rank: Regular Contributor
timestamp: May 02, 2023, 02:49:45 pm
content: Hi iheb,I highly recommend you this reading:https://www.edn.com/test-18-bit-adcs-with-an-ultrapure-sine-wave-oscillator/RegardsFrex

author: iheb
author_rank: Newbie
timestamp: May 03, 2023, 10:58:00 am
content: thank you for your answers I have access to B1500 SMU how ever without a signal generator, i this case how come can you characterize a higher bit adc with a lowerbit DAC (10-bits) the IEEE standards(EEE Standard for Terminology andTest Methods for Analog-to-Digital Converters) states that you have to use a superiour DAC to characterize your ADC. could you please explain how this can be done ?

author: TopQuark
author_rank: Frequent Contributor
timestamp: May 03, 2023, 02:02:43 pm
content: https://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/eval-admx1002.htmlhttps://wiki.analog.com/resources/eval/user-guides/admx/admx100xPerhaps you can use something like this?

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 03, 2023, 07:30:45 pm
content: QuoteWould not need to verify each LSB transition. Higher bit ADCs would not even be feasible to be tested with full walkthrough.The SMU can give you a static test (or DC test) for full scale and INL, assuming the SMU’s accuracy (not the resolution) is better than the DUT.The AC test, with precision oscillator can add more colors - missing codes, various calculated dynamic nonlinearity.What ADC are you testing?

author: iheb
author_rank: Newbie
timestamp: May 05, 2023, 09:38:45 am
content: oh thank you friend , its an STM32 Internal ADC ever tested this one ?

author: Kleinstein
author_rank: Super Contributor
timestamp: May 05, 2023, 09:53:40 am
content: The STM32 internal ADCs are usually relatively fast 12 bit ADC. In this case testing via the histogram method is very viable. One may reach 16 bit noise levels with oversampling, but for characterization the 12 bit part would be enough - the performance with oversampling can than be calculated.

author: Fungus
author_rank: Super Contributor
timestamp: May 05, 2023, 09:59:55 am
content: Quote from: iheb on May 05, 2023, 09:38:45 amI haven't looked but I'm sure there will be performance and linearity graphs in the datasheet.

author: tszaboo
author_rank: Super Contributor
timestamp: May 05, 2023, 10:09:50 am
content: What do you like to test? INL? DNL? Offset? If it works at all? Calibrate it?What will you use it for? DC or AC measurements? Or maybe ratiometric? Slow or fast?You would evaluate it differently because the requirements are different.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 05, 2023, 04:10:08 pm
content: Before you start testing - take a look how the device should be prepared to avoid the usual pitfalls:https://www.st.com/resource/en/application_note/cd00211314-how-to-get-the-best-adc-accuracy-in-stm32-microcontrollers-stmicroelectronics.pdfIf you did the prepwork right, you might get close to the datasheet specs. Probably a bit below it, as the specs reflect an ideal environment of a billion dollar ST lab.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 06, 2023, 01:10:09 pm
content: Quote from: iheb on May 02, 2023, 01:40:40 pmYou can get a pretty good DC accuracy from a PWM output and filtering. Almost any microcontroller can generate an 16bit PWM output, and this has an inherently good INL. To preserve that, you have to use a filter which does not add any DC offset (so a simple two or three stage RC filter works, especially with low leakage capacitors). Another limitation is the reference voltage. The uC's own power voltage is "dirty", so using a buffer and an external reference voltage is needed. If you can use the same reference voltage as the ADC, then this is always the best to do radiometric comparisons.A year and a half ago I started the thread below. I believe it could work quite nicely but I still have not put much effort in it. That thread also has some links to proffesional measurement equipment service manuals (with schematics) that uses this method.https://www.eevblog.com/forum/projects/making-a-pwm-based-voltage-standard/msg3663823/#msg3663823

author: cncjerry
author_rank: Unknown
timestamp: May 13, 2023, 11:54:35 pm
content: Exactly what STM32 part are you testing? If performance is critical, you could use an external ADC as those by LT have known performance characteristics, available board designs, etc.As others have pointed out, generating signals that exceed the performance of the device would be a challenge in itself.

author: coppice
author_rank: Super Contributor
timestamp: May 14, 2023, 12:40:51 am
content: Quote from: Frex on May 02, 2023, 02:49:45 pmTesting with a pure sine wave is not a bad approach, but a much better approach is to use 2 pure sine waves, with a small difference in frequency. Mix the two, digitise the result, and look for intermodulation products in the captured data.