sx8725 Semtech Corporation, sx8725 Datasheet - Page 19

• Manufacturer Part Number: sx8725
• Description: Sx8725 Zoomingadc? For Pressure And Temperature Sensing
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
Input Multiplexers
The ZoomingADC has eight analog inputs AC
define the differential input voltage V
and:
As shown in Table 2, the inputs can be configured in two ways: either as 4 differential channels (V
AC
AC
of the input voltage.
Similarly, the reference voltage is chosen among two differential channels (V
V
V
V1.5 © 2007 Semtech Corp.
REF,ADC
REFN
(RegACCfg5[5:1])
0
0
,..., V
. The control word for the analog input selection is AMUX[4:0]. Notice that the bit AMUX[3] controls the sign
AMUX[4:0]
(common-mode) can be up to the power supply range.
00x00
00x01
10000
10001
10010
10011
= AC_R
IN3
= AC
3
5
- AC_R
– AC
4
AC
AC
), or AC
AC
2
) as shown in Table 3. The selection bit is VMUX. The reference inputs V
V
1
1
AC
AC
AC
0
(V
(V
INP
(V
3
2
3
REF
REF
SS
(RegACCfg5[0])
)
)
)
Table 3 - Analog Reference Input Selection
0
can be used as a common reference, providing 5 signal paths all referred to
VMUX
IN
0
1
V
and reference voltage V
Table 2 - Analog Input Selection
REF
ZoomingADC™ for Pressure and Temperature Sensing
V
AC
AC
,
ADC
IN
V
AC
0
0
INN
(V
(V
0
2
SS
SS
to AC
V
V
)
)
INP
Equation 3
Equation 4
AC_R
AC_R
REFP
V
19
7
REFP
1
V
3
and four reference inputs AC_R
(V
(V
INN
V
BATT
REF
REFN
)
)
(RegACCfg5[5:1])
REF,ADC
AMUX[4:0]
(V)
11000
11001
11010
11011
01x00
01x01
AC_R
AC_R
respectively as:
(V)
V
REFN
0
2
(V
(V
SS
SS
)
)
REF,ADC
AC
AC
V
AC
0
0
INP
(V
(V
2
0
SS
SS
= AC_R
to AC_R
)
)
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1
3
AC
AC
AC
. Let us first
- AC_R
SX8725
V
IN1
1
1
AC
AC
AC
0
INN
(V
(V
(V
REFP
3
2
3
= AC
REF
REF
SS
)
)
)
0
and
1
or
-