MSPM0G1506: About the sampling rate of ADC12 of MSPM0G1506

Hi Mori,

The ADC also need time for conversion. 62.5ns is only the sampling time. 

Best regards,

Cash Hao

Hi Cash Hao.

Thank you for your reply.
As you said, the conversion time seems to be extra.
When I measured the time required for AD conversion, it was 13.6us (16smp).
Therefore, 1000000 / (13.6/16) ≒ 1176471(1Msps).

data sheet
"14-bit effective resolution at 250-ksps with hardware averaging"
I think it's over 250ksps.

"Two simultaneous sampling 12-bit 4-Msps analog-to-digital converters (ADCs) with up to 17 external channels"
It is stated that the 12bit resolution is 4Msps,
Isn't it possible that the sample code "adc12_14bit_resolution" operates at 12bit resolution?

Hi,

Yes, the 12-bit ADC always operates at 12 bit resolution. It is the hardware averaging to increase the resolution to 14-bit.

Best regards,

Cash Hao

Hi Cash Hao.

Thank you for your reply.
The sample code "adc12_14bit_resolution" sets "Hardware Average Configuration" to "16/4" in Syscfg.
Therefore, I think it is set to hardware averaging.
Is the sampling rate limited to "250-ksps"?

Hi，

The sampling rate is limited by the Hardware Average Numerator configuration. For your configuration, it is 16. So, the sampling time for 14bit over sampling is 4Msps/16 = 250ksps.

Best regards,

Cash Hao

Hi Cash Hao.

Thank you for your reply.
It is calculated with 16 times as one sampling. Understood.

Is it possible to get 14bit resolution unless "Hardware Average Numerator" is set to 16?
For example, "Hardware Average Numerator" is 8 and "Hardware Average Denominator" is 2.
Isn't it 14bit resolution?

Hi,

mori.oq said:

For example, "Hardware Average Numerator" is 8 and "Hardware Average Denominator" is 2.
Isn't it 14bit resolution?

It is also 14-bit resolution, However, it only takes 8 samples for averaging. The averaging performance is worse than using 16 samples.

Best regards,

Cash Hao

Hi Cash Hao.

Thank you for your reply.
It's 14bit resolution. Understood.
In this case, it will be 500ksps, and the conversion speed will be faster, but the accuracy cannot be guaranteed, so
Does this mean that you want it to be used at a maximum of 250ksps ("Hardware Average Numerator" is 16)?

For example, if "Hardware Average Numerator" is 128 and "Hardware Average Denominator" is 32,
I think it will be 14bit resolution, but are there any disadvantages other than slower conversion speed?

Hi,

mori.oq said:

In this case, it will be 500ksps, and the conversion speed will be faster, but the accuracy cannot be guaranteed, so
Does this mean that you want it to be used at a maximum of 250ksps ("Hardware Average Numerator" is 16)?

No, wo do not limit the sampling rate here. And the 250ksps is not the limit. It is all depended by the customer about how they want the accuracy and sampling rate.

mori.oq said:

For example, if "Hardware Average Numerator" is 128 and "Hardware Average Denominator" is 32,
I think it will be 14bit resolution, but are there any disadvantages other than slower conversion speed?

There is no other disadvantages other than slow for my view. 

Best regards,

Cash Hao

Hi Cash Hao.

Thank you for your reply.
I found out that there is no limit to the sampling rate at 14-bit resolution.
It means that it is determined by the "Hardware Average Numerator" setting.
Thank you very much for the very good information.