XE8805 SEMTECH [Semtech Corporation], XE8805 Datasheet - Page 95

• Manufacturer Part Number: XE8805
• Description: Data Acquisition MCU
• Manufacturer: SEMTECH [Semtech Corporation]

16.5 Input Multiplexers
The ZoomingADC™ has eight analog inputs AC_A(0) to AC_A(7) and four reference inputs AC_R(0) to
AC_R(3). Let us first define the differential input voltage V
and:
As shown in Table 16-11 the inputs can be configured in two ways: either as 4 differential channels (V
AC_A(1) - AC_A(0),..., V
7 signal paths all referred to AC_A(0). The control word for the analog input selection is AMUX[4:0]. Notice that
the bit AMUX[3] controls the sign of the input voltage.
Similarly, the reference voltage is chosen among two differential channels (V
AC_R(3)-AC_R(2)) as shown in Table 16-12. The selection bit is VMUX. The reference inputs V
(common-mode) can be up to the power supply range.
© Semtech 2006
(RegAcCfg5[5:1])
V
V
IN
REF
AMUX[4:0]
=
V
=
10000
10001
10010
10011
10100
10101
10110
10111
00x00
00x01
00x10
00x11
INP
V
REFP
−
V
INN
−
V
REFN
IN4
= AC_A(7) - AC_A(6)), or AC_A(0) can be used as a common reference, providing
AC_A(1)
AC_A(3)
AC_A(5)
AC_A(7)
AC_A(0)
AC_A(1)
AC_A(2)
AC_A(3)
AC_A(4)
AC_A(5)
AC_A(6)
AC_A(7)
V
(V)
(V)
INP
AC_A(0)
AC_A(2)
AC_A(4)
AC_A(6)
AC_A(0)
Table 16-11. Analog input selection
V
INN
(RegAcCfg5[5:1])
16-9
IN
AMUX[4:0]
and reference voltage V
11000
11001
11010
11011
11100
11101
11110
11111
01x00
01x01
01x10
01x11
(Eq. 3)
(Eq. 4)
AC_A(0)
AC_A(2)
AC_A(4)
AC_A(6)
AC_A(0)
REF1
V
INP
= AC_R(1)-AC_R(0) or V
REF
respectively as:
AC_A(1)
AC_A(3)
AC_A(5)
AC_A(7)
AC_A(0)
AC_A(1)
AC_A(2)
AC_A(3)
AC_A(4)
AC_A(5)
AC_A(6)
AC_A(7)
V
INN
XE8805/05A
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REFP
and V
REF2
IN1
REFN
=
=