What is SAR ADC algorithm?

A successive-approximation ADC is a type of analog-to-digital converter that converts a continuous analog waveform into a discrete digital representation using a binary search through all possible quantization levels before finally converging upon a digital output for each conversion.

How does a SAR ADC work?

The SAR ADC does the following things for each sample: The analog signal is sampled and held. For each bit, the SAR logic outputs a binary code to the DAC that is dependent on the current bit under scrutiny and the previous bits already approximated. The comparator is used to determine the state of the current bit.

What is SAR in microcontroller?

Abstract: Successive-approximation-register (SAR) analog-to-digital converters (ADCs) represent the majority of the ADC market for medium- to high-resolution ADCs. This paper will explain how the SAR ADC operates by using a binary search algorithm to converge on the input signal.

When the comparator output is low SAR will?

If comparator output is LOW, D/A output will be greater than Vin and the MSB will be cleared by the SAR. If comparator output is HIGH, D/A output will be less than Vin and the MSB will be set to the next position (Q7 to Q6) by the SAR.

What is the disadvantage of binary weighted type DAC?

What is the disadvantage of binary weighted type DAC? Explanation: For better resolution of output, the input binary word length has to be increased. As the number of bit increases, the range of resistance value increases.

What is the quickest method of analogue to digital conversion?

Parallel A/D conversion (sometimes called flash conversion) is the fastest technique available and the simplest to understand. However, its practicality is limited to small numbers of bits, since it requires 2N – 1 comparator circuits in order to produce an N-bit digital output.

Why flash type ADC is fastest?

A flash type ADC produces an equivalent digital output for a corresponding analog input in no time. Hence, flash type ADC is the fastest ADC. The 3-bit flash type ADC consists of a voltage divider network, 7 comparators and a priority encoder.

What is a 12 bit ADC?

The number of binary digits (bits) that represents the digital number determines the ADC resolution. ADC has a resolution of one part in 4,096, where 212 = 4,096. Thus, a 12-bit ADC with a maximum input of 10 VDC can resolve the measurement into 10 VDC/4096 = 0.00244 VDC = 2.44 mV.

What is the advantage of binary weighted type DAC?

Binary Weighted Resistor DAC Weighted resistors are used to distinguish each bit from MSB to LSB. Transistors are used to switch between Vref and ground (bit high or low). Advantages: It is Simple in Construction.

When does the SAR control logic move to the next bit?

The SAR control logic then moves to the next bit down, forces that bit high, and does another comparison. The sequence continues all the way down to the LSB. Once this is done, the conversion is complete and the N-bit digital word is available in the register.

What kind of clock is needed for SAR?

The SAR operation is based on binary search algorithm. A SAR logic takes 10 cycles (8bits + 2 extra cycles) to generate one output. Hence, if the sampling rate is 200KHz, 2MHz of clock is required for SAR. In this logic, the bits are represented by the registers D7-D0. In the first cycle, all the registers are set to 0.

How many flops are in the SAR schematic?

The SAR Logic schematic consists of 2N flops (N=8): They are the 8 shift registers and 8 control registers. The Comparator output acts as the control bus logic for computing the output. Fig 6. SAR set/reset logic

What does SAR stand for in successive approximation ADC?

These bit “tests” form the basis of a serial output version SAR-based ADC. Note that the acronym “SAR” actually stands for Successive Approximation Register (the logic block that controls the conversion process), but is universally accepted as the acronym for the architecture itself. SAR ADC TIMING