xe8802 Semtech Corporation, xe8802 Datasheet - Page 120

• Manufacturer Part Number: xe8802
• Description: Data Acquisition Soc With 16+10 Bit Zoomingadc? Embedded Risc Controller And Lcd Driver
• Manufacturer: Semtech Corporation

Similarly, the reference voltage is chosen among two differential channels (V
AC_R(3)-AC_R(2)) as shown in Table 17-12. The selection bit is VMUX. The reference inputs V
(common-mode) can be up to the power supply range.
17.6
As seen in Figure 17-1, the zooming function is implemented with three programmable gain amplifiers (PGA).
These are:
•
•
•
All gain and offset settings are realized with ratios of capacitors. The user has control over each PGA activation
and gain, as well as the offset of stages 2 and 3. These functions are examined hereafter.
© Semtech 2006
(RegAcCfg5[5:1])
PGA1: coarse gain tuning
PGA2: medium gain and offset tuning
PGA3: fine gain and offset tuning
Programmable Gain Amplifiers
AMUX[4:0]
00x00
00x01
00x10
00x11
10000
10001
10010
10011
10100
10101
10110
10111
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
(RegAcCfg5[0])
INP
Table 17-12. Analog Reference input selection
VMUX
ENABLE[3:0]
AC_A(0)
AC_A(2)
AC_A(4)
AC_A(6)
AC_A(0)
0
1
Table 17-11. Analog input selection
V
Table 17-13. ADC & PGA enabling
XE8802 Sensing Machine Data Acquisition MCU
INN
xxx0
xxx1
xx0x
xx1x
x0xx
x1xx
0xxx
1xxx
AC_R(1)
AC_R(3)
(RegAcCfg5[5:1])
V
17-8
REFP
AMUX[4:0]
with ZoomingADC™ and LCD driver
01x00
01x01
01x10
01x11
11000
11001
11010
11011
11100
11101
11110
11111
PGA1 disabled
PGA2 disabled
PGA3 disabled
PGA1 enabled
PGA2 enabled
PGA3 enabled
ADC disabled
ADC enabled
AC_R(0)
AC_R(2)
Block
V
REFN
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
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
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REFP
and V
REF2
REFN
=