TMS320F28335 vs TMS320F28377D sample and hold

Hi Adam,

Using dual S+H, the F28335 can sample two voltages at exactly the same time.  This is accomplished by charging one S+H capacitor (on an 'A' channel) with the first voltage while also charging a separate S+H capacitor (on a 'B' channel) with the second voltage.  After both voltages are captured on the two capacitors, the voltages are converted to a digital value sequentially in the ADC.  First the 'A' S+H capacitor is converted, then the 'B' S+H is converted.  The voltages were sampled at the same time, and processed through the same converter, so they are correlated extremely well.

The ADC module on F28377D has only one S+H; it samples one voltage at a time and then converts it.  However, there are 4 ADCs on the device (F28335 has only one ADC), and they can be triggered at the same time, effectively allowing 4 voltages to be sampled at exactly the same time.  Note that in this case, the temporal correlation is still extremely good, but the voltages were processed through 4 separate ADCs.  Since these 4 ADCs are the same design and on the same silicon die, correlation is very good.    

Note that F28335 is a single-ended ADC, while F28377D can use either single-ended or differential signals (when using 12-bit resolution) or must use differential signals (when using 16-bit resolution).