XE8805 SEMTECH [Semtech Corporation], XE8805 Datasheet - Page 96

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

16.6
As seen in Figure 16-1, 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
PGA1: coarse gain tuning
PGA2: medium gain and offset tuning
PGA3: fine gain and offset tuning
Programmable Gain Amplifiers
(RegAcCfg5[0])
Table 16-12. Analog Reference input selection
PGA2_GAIN[1:0]
VMUX
ENABLE[3:0]
0
1
PGA1_GAIN
Table 16-13. ADC & PGA enabling
Table 16-14. PGA1 Gain Settings
Table 16-15. PGA2 gain settings
xxx0
xxx1
xx0x
xx1x
x0xx
x1xx
0xxx
1xxx
00
01
10
11
0
1
AC_R(1)
AC_R(3)
16-10
V
REFP
PGA1 disabled
PGA2 disabled
PGA3 disabled
PGA1 enabled
PGA2 enabled
PGA3 enabled
ADC disabled
ADC enabled
PGA1 Gain
PGA2 Gain
GD
GD
AC_R(0)
AC_R(2)
Block
V
1
2
REFN
10
10
1
1
2
5
(V/V)
(V/V)
XE8805/05A
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