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Visitor narwalajit
Visitor
28,615 Views
Registered: ‎05-18-2012

ADC with multiplexing for ML507 FPGA

Hi guys,

I have an ML507 FPGA and analog signals (+/- 5V, 100mA) which are around 40 in number.

 

I need to design an interface between the circuit and the FPGA with ADCs along with multiplexing (can not stress enough about the multiplexing since I have high humber if inputs and limited GPIOs). 

 

 

It would be great if anyone could help me with this query?

 

PS: Please also let me know if you need any additonal details to answer this.

 

Thanks,

 

AJ

 

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3 Replies
Advisor joelby
Advisor
28,597 Views
Registered: ‎10-05-2010

Re: ADC with multiplexing for ML507 FPGA

You haven't really stated what your analog requirements are. Do you need 40 simultaneous sampling channels, or can you multiplex the analog inputs? What are your resolution and sample rate requirements?

 

You can get ADCs with 16 (maybe even more) input channels such as the AD7490. These kinds of parts tend to have serial (e.g. SPI) output so you could easily connect many of these to an ML507.

 

If you need to simultaneously sample 40 channels at 16-bit, 100 MSPS then it should be possible but will be a bit more of a design challenge.

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Visitor narwalajit
Visitor
28,592 Views
Registered: ‎05-18-2012

Re: ADC with multiplexing for ML507 FPGA

Hi,

I have simultaneous 40 analog signals to be sampled. Since I want to economize on the GPIOs hence I am thinking about multiplexing (which will lead to delay for every signal to be sent to algorithm simultaneously... but that is fine).

The sampling rate is close to 2kHz (+/- a few 100 Hz).

The ADC resolution can be as low as 12 bit.

One correction from the last post though, the analog signals are +/- 10 V, 100 mA.

Please let me know what do you think about this.

Thanks,
AJ
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Advisor joelby
Advisor
28,581 Views
Registered: ‎10-05-2010

Re: ADC with multiplexing for ML507 FPGA

From an FPGA point of view, there's nothing too difficult about this task.

 

For the ADC, use the parametric search function provided by your favourite ADC manufacturers. I found one made by Analog Devices called the AD7607 which provides 8, 14-bit simultaneous sampling inputs at 200 KSPS, serial output, and a +/- 10V analog input. You'd need 5 of these to get 40 channels, but that shouldn't be much of a problem.

 

Typically you would need to design some sort of analog front end circuitry - coupling, amplification or attenuation, filtering, buffering, impedance matching, etc. This is a bit out of the scope of this forum though.

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