AN4207 Sigma-delta (SD) vs. successive approximation register (SAR) analog-to-digital convert-

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Sigma-delta (SD) vs. successive approximation

register (SAR) analog-to-digital converters

Analog to digital converters come in different architectures to be able to address the needs

of different applications. The main types available in the market are:

Successive approximation register (SAR) ADC: Successive-approximation-register

(SAR) analog-to-digital converters (ADCs) are frequently used in embedded systems, with

sample rates of less than 5 megasamples per second (Msps). Their resolution ranges from

8 to 16 bits. This type of ADC is used in industrial control applications.

Sigma-delta ADC (SDADC): Sigma-Delta analog-to-digital converters (ADCs) are used in

lower speed applications requiring high resolution. The resolution may attain 24 bits by

oversampling but the sampling rate is limited to only a few ksps.

Flash ADC: Flash analog-to-digital converters, are the fastest type of analog to a digital

converter. They are suitable for applications requiring a very high sampling rate. However,

flash converters have low resolution (12-bits). This type of ADC is used in oscilloscopes.

The Figure 11 gives an overview of the different ADC architectures, comparing their

resolution and sampling rate.

Figure 11.

ADC architecture vs. resolution and sampling rate

The STM32F37x/38x devices have two types of embedded ADCs: 12-bit SAR ADC and 16-

bit SDADC.

The Table 4 summarizes the differences between the two types of ADC.

24

16

8

12

Sample rate (sample/s)

100 k

5 M

5 G

Sigma Delta

SAR

Flash

MSv31138V1