sx8724s Semtech Corporation, sx8724s Datasheet - Page 52

• Manufacturer Part Number: sx8724s
• Description: Zoomingadc For Sensing Data Acquisition
• Manufacturer: Semtech Corporation

Revision 1.0
© Semtech
11.2 Frequency Response
The incremental ADC is an over-sampled converter with two main blocks: an analog modulator and a low-pass digital
filter. The main function of the digital filter is to remove the quantization noise introduced by the modulator. This filter
determines the frequency response of the transfer function between the output of the ADC and the analog input V
Notice that the frequency axes are normalized to one elementary conversion period OSR / fs. The plots of
page 53
performed. In particular, notches appear for N
and are repeated every fs / OSR.
Information on the location of these notches is particularly useful when specific frequencies must be filtered out by the
acquisition system. This chip has no dedicated 50/60 Hz rejection filtering but some rejection can be achieved by using
Equation 27
ADVANCED COMMUNICATIONS & SENSING
also show that the frequency response changes with the number of elementary conversions N
and setting the appropriate values of OSR, fs and N
Rejection [Hz]
60
50
f
February 2011
NOTCH
=
------------------------------------ -
OSR N
f
61
61
61
53
46
46
NOTCH
Table 37. 50/60 Hz Line Rejection Examples
⋅
i f
⋅
ELCONV
s
[Hz]
ELCONV
fs [kHz]
125
250
500
62.5
62.5
125
>= 2 These notches occur at:
For
Equation 27
Page 52
ELCONV
ZoomingADC for sensing data acquisition
i
OSR [-]
1024
1024
1024
1024
1024
1024
.
=
1 2 … N
, ,
(
ELCONV
N
2
4
8
8
4
8
ELCONV
–
[-]
1
SX8724S
)
www.semtech.com
DATASHEET
ELCONV
Figure 34,
IN
.