OSR

1

10

100

1000

0

2

4

6

8

10

12

14

16

D040

sinc3

sinc2

sinc1

3

OSR

1

1

z

H z

1

z

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·

¨

¸

¨

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27

AMC1306E05, AMC1306E25, AMC1306M05, AMC1306M25

www.ti.com

SBAS734C – MARCH 2017 – REVISED JANAURY 2020

Product Folder Links: AMC1306E05 AMC1306E25 AMC1306M05 AMC1306M25

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Copyright © 2017–2020, Texas Instruments Incorporated

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

9.1.1 Digital Filter Usage

The modulator generates a bitstream that is processed by a digital filter to obtain a digital word similar to a

conversion result of a conventional analog-to-digital converter (ADC). A very simple filter, built with minimal effort

and hardware, is a sinc3-type filter, as shown in Equation 2:

(2)

This filter provides the best output performance at the lowest hardware size (count of digital gates) for a second-

order modulator. All the characterization in this document is also done with a sinc3 filter with an oversampling

ratio (OSR) of 256 and an output word width of 16 bits.

The effective number of bits (ENOB) is often used to compare the performance of ADCs and ΔΣ modulators.

Figure 55 shows the ENOB of the AMC1306 with different oversampling ratios. In this document, this number is

calculated from the SINAD by using Equation 3:

SINAD = 1.76 dB + 6.02 dB × ENOB

(3)

Figure 55. Measured Effective Number of Bits versus Oversampling Ratio

An example code for implementing a sinc3 filter in an FPGA is discussed in the Combining the ADS1202 with an

FPGA Digital Filter for Current Measurement in Motor Control Applications application note, available for

download at www.ti.com.