SX8801IRXXMLTRT View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'SX8801IRXXMLTRT' PDF : 135 Pages View PDF
XE8801A – SX8801R
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 VIN and reference voltage VREF respectively as:
VIN = VINP −VINN
(V)
(Eq. 3)
and:
VREF = VREFP − VREFN
(V)
(Eq. 4)
As shown in Table 16-11 the inputs can be configured in two ways: either as 4 differential channels (VIN1 = AC_A(1)
- AC_A(0),..., VIN4 = AC_A(7) - AC_A(6)), or AC_A(0) can be used as a common reference, providing 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.
AMUX[4:0]
(RegAcCfg5[5:1])
00x00
00x01
00x10
00x11
10000
10001
10010
10011
10100
10101
10110
10111
VINP
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)
VINN
AC_A(0)
AC_A(2)
AC_A(4)
AC_A(6)
AC_A(0)
AMUX[4:0]
(RegAcCfg5[5:1])
01x00
01x01
01x10
01x11
11000
11001
11010
11011
11100
11101
11110
11111
VINP
AC_A(0)
AC_A(2)
AC_A(4)
AC_A(6)
AC_A(0)
VINN
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)
Table 16-11. Analog input selection
Similarly, the reference voltage is chosen among two differential channels (VREF1 = AC_R(1)-AC_R(0) or VREF2 =
AC_R(3)-AC_R(2)) as shown in Table 16-12. The selection bit is VMUX. The reference inputs VREFP and VREFN
(common-mode) can be up to the power supply range.
VMUX
(RegAcCfg5[0])
0
1
VREFP
AC_R(1)
AC_R(3)
VREFN
AC_R(0)
AC_R(2)
Table 16-12. Analog Reference input selection
© Semtech 2005
16-8
www.semtech.com
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