Contents
What are the important factors to consider in an ADC conversion?
Considerations
- Availability/Cost.
- Precision/Resolution (number of bits)
- Accuracy (error in conversion)
- Speed (time for one conversion, different from clock speed)
- Voltage Range.
- Multiplexing.
- Ease of Use.
What factors contribute to ADC noise error?
Unfortunately, numerous factors degrade the ADC’s ideal performance resulting in a lower SNR value and higher effective noise figure value. These factors include thermal noise, clock jitter (especially for higher input frequencies having high slew rates), and subranging errors.
What is ADC gain error?
Gain error is defined as the full-scale error minus the offset error (Figure 5). Full-scale error is measured at the last ADC transition on the transfer-function curve and compared against the ideal ADC transfer function. Typically, the gain error is much worse when an on-chip reference is used.
Why do we need differential signals in an ADC converter?
For best performance, reduce the input signal range to ensure that the ADC input range is not exceeded. Another key advantage of differential signals is the increased dynamic range. With power supplies dropping to 3.3V and lower, design engineers are looking for ways to achieve greater input dynamic range.
How is aliasing prevented in an ADC circuit?
A practical means of preventing aliasing is to place a low-pass filter before the input of the ADC, to block any signal frequencies greater than the practical limit. This way, the ADC circuitry will be prevented from seeing any excessive frequencies and thus will not try to digitize them.
What causes common mode on an ADC input?
A DC common-mode voltage appearing across an ADC input has the same effect as a DC input offset. Normally, the sensor signal and ground wire are in close proximity physically and will couple in common-mode noise. The largest source of common-mode noise is often 50/60Hz noise from power lines.
How is a sensor interfacing with an ADC?
Interfacing a sensor to an ADC requires matching the sensor/signal conditioning output with the ADC input. Voltage output sensors provide either a single-ended or differential output. For single-end signals, all the inputs are referenced to system ground.