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How is the voltage reference affects ADC performance, Part 2?
where “Code” is the ADC output code in decimal form, VIN is the analog input voltage to the ADC, n is the number of ADC output bits, and VREF is the analog value of the ref-erence voltage to the ADC. This formula shows that any initial error or noise in the reference voltage translates to gain error in the code output of the ADC.
What is the source resistance of an ADC?
An ADC operating at 1Million conversions per second, with Cref of 10pF and with VREF of +5volts, needs F * C * Vref average current; that is 1e6 * 1e-11 * 5, or 5e-5 amps or 50 microAmps. Thus the source resistance of VREF is an error, appearing in FullScale accuracy.
What is the function of Vref in standalone ADC?
In standalone ADC’ Vref is used as a reference point to determine the relative (in voltage) size of an LSB. Usually the formula is something to the effect of: VREF has the burden of supplying the fast surges of current, as the ADC plows through its binary-search approximation.
How to connect temperature sensor to ADC channel 10?
If my understanding is correct, then I would connect a temperature sensor to physical pin 10 (aka ADC channel 0), ensure that sensor has a voltage of ~3.3v. Then for reference, connect the same input somewhere on the blue-pill so it can do the conversion.
Why do you need a reference buffer for multiple ADCs?
A reference buffer is very useful for driving multiple ADCs from one reference, as is the case in simultaneous-sampling applications, such as that shown in Figure 6. Figure 6. Reference circuit driving multiple ADCs. Each ADC reference input has its own reservoir capacitor placed as close as possible to the reference input pin.
How is the ADC used in an embedded system?
An embedded system uses the ADC to collect information about the external world (data acquisition system.) The input signal is usually an analog voltage, and the output is a binary number. The ADC precision is the number of distinguishable ADC inputs (e.g., 4096 alternatives, 12 bits).
How is the resolution of an ADC determined?
For example if we use a slide pot to measure distance, the range of that pot might be 0 to 1.5cm. If there is no electrical noise and we use a 12-bit ADC, then the theoretical resolution is 1.5cm/4095, or about 0.0004 cm. In most systems, the resolution of the measurement is determined by noise and not the number of bits in the ADC.