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Altera_Forum
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8 years ago

DC coupled ADC (HSMC)

I bought a "Terasic Cyclone V GX Starter Kit" and I have to process a analog signal. I bought a "Terasic Highspeed AD/DA Card" and connected it via HSMC. Unfortunatly I realized that the inputs are t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
8 years ago

The 1.65 V bias is generated by dividing 3.3 V supply with 1k + 1k voltage divider, see ADDA card schematic. It's usual to bias differential input ADC at the center of analog supply voltage for best linearity.

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Does this mean that I have to connect VINn to (0V) ground to get an input range of -1 to 1V?

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That's not possible, you need to consider ADC input voltage range. 0 V (or may be -0.2 or -0.3 V) is the most negative voltage that can be processed by an ADC input pin.

If you read the datasheet thoroughly, you'll notice that single ended operation gives reduced performance anyway. For DC capable operation of a differential input ADC, you preferably use a fully differential amplifier, see e.g. AD9248 evaluation board schematic.