sx8723c Semtech Corporation, sx8723c Datasheet - Page 28

• Manufacturer Part Number: sx8723c
• Description: Zoomingadc For Sensing Data Acquisition
• Manufacturer: Semtech Corporation

Revision 1.01
© Semtech
7.7 Analog-to-Digital Converter (ADC)
The main performance characteristics of the ADC (resolution, conversion time, etc.) are determined by three
programmable parameters. The setting of these parameters and the resulting performances are described later.
7.7.1 Conversion Sequence
A conversion is started each time the bit Start or the Def bit is set. As depicted in
digital conversion sequence is made of a set of N
step. Each elementary conversion is made of (OSR+1) over-sampling periods Ts=1/fs, i.e.:
The result is the mean of the elementary conversion results. An important feature is that the elementary conversions
are alternatively performed with the offset of the internal amplifiers contributing in one direction and the other to the
output code. Thus, converter internal offset is eliminated if at least two elementary sequences are performed (i.e. if
N
ADVANCED COMMUNICATIONS & SENSING
ELCONV
fs :
OSR :
N
ELCONV
Conversion index
>= 2). A few additional clock cycles are also required to initiate and end the conversion properly.
Offset
:
Init
Note
Over-sampling frequency
Over-Sampling Ratio
Number of Elementary Conversions
Elementary
Conversion
January 2011
1
+
The internal bandgap reference state may be forced High or Low, or may be set
to toggle during conversion at either the same rate or half the rate of the
Elementary Conversion. This may be useful to help eliminate bandgap related
internal offset voltage and 1/fs noise.
Figure 14. Analog-to-Digital Conversion Sequence
Elementary
Conversion
2
-
T
ELCONV
ELCONV
Equation 13
=
Page 28
T
CONV
(
elementary incremental conversions and a final quantization
OSR
+
Elementary
Conversion
1
N
/ )
ELCONV
ZoomingADC for sensing data acquisition
f
+
S
-1
[
s
]
Elementary
Conversion
Figure
N
ELCONV
-
14, a complete analog-to-
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SX8723C
End
DATASHEET
Conversion
Result