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What is role of VREF in ADC and DAC?
Advanced Member level 2. vref is the maximum output that DAC shall give when the biggest binary input word (0xFF for 8 bits) is given. vref is the maximum voltage for which an ADC shall give the biggest binary output word (0xFF for 8 bits).
What is the effect of VREF voltage on ADC resolution?
The stability of the voltage provided as VREF over varying temperatures is very important. If not, then the ADC will give results that are skewed around the temperature at which it was first calibrated. VREF should also be a value that is close to the maximum value that the analog input on the ADC will see.
What is shunt voltage reference?
A shunt voltage reference only requires two terminals and is functionally similar to a Zener diode where the voltage drop across the device is constant after reaching a minimum operating current through the device. The resistor sets the total current sourced by the input supply as a function of the supply voltage.
What is the use of VREF pin in ADC?
Voltage references (VREF) are beneficial and often necessary for high-accuracy signal chain applications. This is because a standard signal chain contains a data converter, such as the Analog-to-digital converter (ADC) or Digital-to-analog converter (DAC), which measure or create a precise signal.
What is the difference between ADC and DAC?
An ADC takes an analog signal and converts it into a binary one, while a DAC converts a binary signal into an analog value.
For instance, a signal at its highest value (pegged) at 3.3 V into the analog input to the ADC should relate back to a V REF of 3.3 V into the ADC. It is possible to compensate for variations in VREF using software and thereby calibrating the ADC, but this creates another potentially intensive task for the processor.
Is the reference voltage External to the ADC?
The voltage reference is external to the ADC, and along with an amplifier to drive the reference, contributes to the overall system noise. For microcontrollers (MCUs) that have integrated (internal) ADCs, you may or may not have control over the reference voltage.
Which is better reference voltage or shunt voltage?
The voltage reference should have noise value specifications lower than the ADC. The topology of the series voltage reference (as opposed to a shunt voltage reference) favors a better initial voltage performance and low drift over temperature. [i]
Which is better Vref or ppm / °C?
In short, the lower the number of ppm/°C, the better. Additionally, the initial output voltage accuracy of VREF should be low, in the range of 0.5% or less for precision ADC applications.