XE88LC01MI000 ETC1 [List of Unclassifed Manufacturers], XE88LC01MI000 Datasheet - Page 32

• Manufacturer Part Number: XE88LC01MI000
• Description: Sensing Machine 16 + 10 bit Data Acquisition Ultra Low-Power Microcontroller
• Manufacturer: ETC1 [List of Unclassifed Manufacturers]

Table 8.9:
8.14 Frequency Response
32
Figure 8.22:
V
V
Supply
DD
DD
= 5V
= 3V
GAIN = 1
79
72
PSRR (n = 16 bits, V
The incremental ADC of the XE88LC01 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 re-
move the quantization noise introduced by the modulator. As shown below, this filter deter-
mines the frequency response of the transfer function between the output of the ADC and the
analog input V
period OSR/f
number of elementary conversions N
N
and are repeated every f
Information on the location of these notches is particularly useful when specific frequencies
must be filtered out by the acquisition system. For example, consider a 5Hz-bandwidth, 16-bit
sensing system where 50Hz line rejection is needed. Using the above equation and the plots
below, we set the 4th notch for N
frequency is then calculated as f
also good attenuation of 50Hz harmonics.
Power supply rejection ratio (PSRR)
f
ELCONV
NOTCH
) (
GAIN =5
i
≥ 2. These notches occur at:
78
79
=
OSR
S
IN
. The plots below also show that the frequency response changes with the
105
100
95
90
85
80
75
70
65
60
. Notice that the frequency axes are normalized to one elementary conversion
i
⋅
⋅
N
IN
GAIN = 10
f
ELCONV
VDD=3V
VDD=5V
S
= V
1
100
90
S
REF
/OSR.
(Hz)for
= 2.5V, f
5
PGA Gain [V/V]
ELCONV
S
GAIN = 20
= 20.48kHz for OSR = 512. Notice that this choice yields
i
99
90
ELCONV
10
S
=
= 500kHz)
1
2 ,
= 4 to 50Hz, i.e. 1.25⋅f
,...,
20
performed. In particular, notches appear for
(
N
GAIN =100
ELCONV
97
86
100
−
) 1
Unit
dB
dB
S
/OSR = 50Hz. The sampling
Data Sheet XE88LC01
Data Acquisition Microcontroller
D0202-60