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ADSP-2199x, ADC details

Question asked by enrique@brazil on Feb 22, 2013
Latest reply on Mar 15, 2013 by Harshit.Gaharwar

Hi friends,

I'd like to get some clarifying explanation on ADSP-2199x, ADC conversion range.

As becomes clear out of Figure19-2 (see attached file) of document ADSP-2199x Mixed Signal DSP Controller - Hardware Reference(50171261290224ADSP_2199x_Hardware_Reference) and Table 19-1. Data Register Format for ADC of ADSP-2199 of that very document (see attached file) the input voltage range to the DAC core (see attached file) varies between -Vref and +Vref.

Nevertheless, all flash ADC circuits I've seen in the literature convert voltages in the positive voltage range (f. i., between 0 and +Vref volts); see please attached file flashADC.jpg.

Since analog power supply to the DSP is: AVDD (2 pins), Analog Supply Voltage and AVSS (2 pins), Analog Ground, how could conversion with voltages in the negative voltages range take place?

Please explain or, otherwise, detail more the circuitry involved within the 14-bit pipeline flash ADC depicted in file: Figure 19-1Functional block diagram of the ADC system of theADSP-2199x.jpg (attached).