SX8725C View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'SX8725C' PDF : 68 Pages View PDF
SX8725C
ZoomingADC for sensing data acquisition
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
resolution is truncated to 16 bit by the output register size, it may make sense to set OSR and NELCONV to higher values
in order to reduce the influence of the thermal noise in the PGA .
Table 17. Resolution1 vs. SetOsr and SetNelconv settings
SetOsr
SetNelconv control bits
control bits
‘00‘
‘01‘
‘10‘
‘11’
‘000‘
6
7
8
9
‘001‘
8
9
10
11
‘010‘
10
11
12
13
‘011‘
12
13
14
15
‘100‘
14
15
16
16
‘101‘
16
16
16
16
‘110‘
16
16
16
16
‘111‘
16
16
16
16
1. In shaded area, the resolution is truncated to 16 bits due to output register size RegA-
COut[15:0]
7.7.6 Conversion Time & Throughput
As explained in Figure 15, conversion time is given by:
TCONV = (NELCONV ⋅ (OSR+1) +1) / fS [s]
Equation 17
and throughput is then simply 1/TCONV. For example, consider an over-sampling ratio of 256, 2 elementary conversions,
and a sampling frequency of 500 kHz (SetOsr = "101", SetNelconv = "01" and SetFs = "00"). In this case, using Table 18,
the conversion time is 515 sampling periods, or 1.03ms. This corresponds to a throughput of 971Hz in continuous-time
mode. The plot of Figure 16 illustrates the classic trade-off between resolution and conversion time.
Table 18. Normalized conversion time (Tconv x fs) vs. SetOsr and SetNelconv settings1
SetNelconv control bits
SetOsr bits
NELCONV
OSR
‘00‘
‘01‘
‘10‘
‘11‘
1
2
4
8
‘000‘
10
19
37
73
‘001‘
18
‘010‘
34
‘011‘
66
35
69
137
67
133
265
131
261
521
Revision 1.01
© Semtech
January 2011
Page 31
www.semtech.com/products/
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