AMC1305L25-Q1 Datasheet, PDF (24/38 Pages) Texas Instruments – High-Precision, Reinforced Isolated Delta-Sigma Modulators

AMC1305L25-Q1, AMC1305M05-Q1, AMC1305M25-Q1
SBAS797 – FEBRUARY 2017
9 Application and Implementation
www.ti.com
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, built with minimal effort
and hardware, is a sinc³-type filter, as shown in Equation 2:
H (z)
¨¨©§
1
1
z ^OSR
z¹
¸¸¹·³
(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 over-sampling
ratio (OSR) of 256 and an output word width of 16 bits.
SNR 1.76dB 6.02dB* ENOB
(3)
16
14
12
10
8
6
4
sinc1
2
sinc2
sinc3
0
1
10
100
1000
OSR
D053
Figure 53. Measured Effective Number of Bits versus Oversampling Ratio
An example code for an implementation of a sinc³ filter in an FPGA, see the application note Combining
ADS1202 with FPGA Digital Filter for Current Measurement in Motor Control Applications (SBAA094), available
for download at www.ti.com.
24
Submit Documentation Feedback
Copyright © 2017, Texas Instruments Incorporated
Product Folder Links: AMC1305L25-Q1 AMC1305M05-Q1 AMC1305M25-Q1