AMC1303E0510 Datasheet, PDF (23/40 Pages) Texas Instruments – Small, High-Precision, Reinforced Isolated Delta-Sigma Modulators with Internal Clock

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AMC1303E0510, AMC1303M0510, AMC1303E0520, AMC1303M0520
AMC1303E2510, AMC1303M2510, AMC1303E2520, AMC1303M2520
SBAS771 – JUNE 2017
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 bit stream 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, shown in Equation 2,
built with minimal effort and hardware, is a sinc³-type filter:
Hz
§
¨¨©
1
1
z
OSR
z¹
·³
¸¸¹
(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 done with a sinc³ filter with an oversampling ratio
(OSR) of 256 and an output word size of 16 bits.
The effective number of bits (ENOB) is often used to compare the performance of ADCs and ΔΣ modulators.
shows the ENOB of the AMC1303 with different oversampling ratios. In this document, Equation 3 calculates this
number from the SNR:
ENOB ^{SNR 1.76 dB}
6.05 dB
(3)
16
14
12
10
8
6
4
sinc³
2
sinc²
sinc¹
0
1
10
100
1000
OSR
D040
Figure 45. Measured Effective Number of Bits versus Oversampling Ratio
An example code for implementing a sinc³ filter in an FPGA is discussed in application note Combining ADS1202
with FPGA Digital Filter for Current Measurement in Motor Control Applications, available for download at
www.ti.com.
Copyright © 2017, Texas Instruments Incorporated
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