TMS320F28020 ADC analog bandwidth

Frank,

By bandwidth, do you mean minimum conversion time or samples/sec?  If so, there is a "Hardware Features" table in the datasheet which provides this information.  According to this table, the F28020 ADC can support 2 MSPS.

-Tommy

Frank,

Here is some of the feedback I got from the factory regarding your question:

"There is no attenuation of a sine wave into the ADC, even if the signal is so fast that the maximum ADC sample rate is right at the Nyquist frequency.  Any faster than that, we have no experimental data, and the best thing we can provide is the impedance mode of the ADC input which is in the datasheet."

The impedance mode of the TMS320F28020 12-bit ADC is discussed on page 128 of the Data Manual.

TMS320F28020 Data Manual: http://www.ti.com/lit/ds/sprs230m/sprs230m.pdf#page=128 

Let us know if you need anything else.

When I have dealt with data converters in the past, the analog bandwidth is specified as a frequency and it is the maximum frequency that the data converter can perform conversions on.   I looked at the data converter section of the data manual you specified.  Maybe I am asking this question incorrectly.  Since you are implying that the Nyquist frequency is the max signal that has been tested, can you tell me what that frequency is?  I am certainly no data converter expert which is evident with the questions I am asking but neither is my customer.

Thank you,

Frank

No, I mean the max input signal (given as a frequency) that the ADC on the F28020 can perform conversions on

I think the parameter you want to look at MSPS (mega-samples per second).  The 28020 can do 2MSPS.

The Nyquist frequency is the minimum (theoretical) sampling frequency necessary to reconstruct an AC signal, and is simply 2x the signal frequency.  For example the nyquist frequency for a 1MHz signal is 2MHz, which means to reconstruct a 1MHz signal you must theoretically sample at at least 2MSPS (but in reality you want to sample faster).  

When we said that the 2802x bandwidth had been tested up to the Nyquist frequency, we meant that even a 1MHz sine wave for 28020 (the maximum you could hope to reconstruct with the device) does not experience analog attenuation due to the 2802x input impedance characteristics.       

Hopefully this helps.  We should be able to provide more guidance as to whether the device meets the customer requirements with more specifics of what kind of signal(s) the customer intends to sample.  

Hello Devin,

Thank you for your input but no I don't need to know the speed of this ADC. 

I just looked at an ADC (ADS4226) and one of the parameters is Analog input bandwidth and the value for this particular ADC is 600MHz.  And the speed of this ADC is 160MSPS.  So I am not talking about the speed of the ADC on theTMS320F28020, I am talking about the analog input bandwidth.  So that is what my customer is asking about that is not listed anywhere he or I could find in the datasheet or the datamanual.  So what is the analog input bandwidth of the ADC of the TMS320F28020?

Thank you,

The bandwidth is > 1MHz based on limited experimental data.  How much greater is unknown;  we do not spec this number in the datasheet and likely will not in the future.