Max internal ADC clk in ARM processors

Thread Starter

matriX1500

Joined May 16, 2019
3
Hi every one,
I'm designing a simple oscilloscope. I need 48 MSPS ADC. For cost considerations, i prefer to use an ARM-Based micro controller with an internal ADC. Is there a ARM-Based micro controller with an internal 48 MSPS ADC?
Thanks
 

danadak

Joined Mar 10, 2018
4,057
Typical 18 clocks / sample conversion, 12 bits, implies 864 Mhz clock.

Of course if 8 bits thern it scales lower, still pretty aggressive clock.


Regards, Dana.
 

MrChips

Joined Oct 2, 2009
22,886
Typical 18 clocks / sample conversion, 12 bits, implies 864 Mhz clock.

Of course if 8 bits thern it scales lower, still pretty aggressive clock.


Regards, Dana.
I don't know how you arrived at that conclusion. 18 x 12 x 4 = 864.
Are you assuming that the ADC has a serial interface or conversion mechanism?
 

MrChips

Joined Oct 2, 2009
22,886
Hi every one,
I'm designing a simple oscilloscope. I need 48 MSPS ADC. For cost considerations, i prefer to use an ARM-Based micro controller with an internal ADC. Is there a ARM-Based micro controller with an internal 48 MSPS ADC?
Thanks
The fastest internal ADC I have encountered is 12 bits @ 5Msps.
 

danadak

Joined Mar 10, 2018
4,057
I don't know how you arrived at that conclusion. 18 x 12 x 4 = 864.
Are you assuming that the ADC has a serial interface or conversion mechanism?

SAR is typically N clocks + some clocks for sample acquisition and other
pre conversion needs. I know of one ARM family this is 18 clocks for
12 bit conversion.

The equation should have been 18 clocks/conversion x 48 MSPS = 864.


Regards, Dana.
 

Thread Starter

matriX1500

Joined May 16, 2019
3
Excuse me, I can't understand what are you saying. Can you offer a micro controller with a single channel 48 MSPS internal ADC?
 

danadak

Joined Mar 10, 2018
4,057
Not that I know of. But you also need to indicate how many bits, 8, 10, 12 ?

In prior post trying to compute what the on chip clock frequency has to be for the SAR.
If you want X SPS, you look up how many clock cycles required to do 1 SPS, and multiply
that X SPS to get onchip clock frequency. The SAR I am thinking of does 1 SPS in 18 clocks.
So 18 clocks/sample x 48M samples/sec = 864 M clocks/sec = 864Mhz on chip. This particular
chip is good for 1 MSPS.


Regards, Dana.
 

Thread Starter

matriX1500

Joined May 16, 2019
3
I need 8Bit adc.
But what is your calculations shows is only about processors clk, what about processors internal ADC? It should support 48 MSPS.
 

george4657

Joined Apr 12, 2016
15
The stm32f303 has 4 adc with clock of 72 mhz. The problem is the system used is "successive approximation" , that is a sample is taken at 2 clock pulses and then 8 more clock pulses are needed to calculate the value of the pulse. This means the maximum frequency read is 7.2 mhz at 72 mhz clock.
If you interleave 2 adc you can double this to 14.4 mhz
Interleavening is sample value and start calculation,half way to finish calculation start a sample on second adc.
In theory you could interleave 4 adc to get 24 mhz.
The fastest I have heard of any processor is 20 mhz
 
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