SX8722I070LF SEMTECH [Semtech Corporation], SX8722I070LF Datasheet - Page 58

• Manufacturer Part Number: SX8722I070LF
• Description: High gain acquisition for sensor interface
• Manufacturer: SEMTECH [Semtech Corporation]

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 42 The selection bit is VMUX. The reference inputs VREFP and VREFN (common-
mode) can be up to the power supply range.
12.7. Programmable Gain Amplifiers
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.
12.7.1. PGA & ADC Enabling
Depending on the application objectives, the user may enable or bypass each PGA stage. This is done according to the
word ENABLE and the coding given in Table 43. To reduce power dissipation, the ADC can also be inactivated while idle.
12.7.2. PGA1
The first stage can have a buffer function (unity gain) or provide a gain of 10 (see Table 44). The voltage V
PGA1 is:
ACS - Revision 4.2
©2008 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
PGA1: coarse gain tuning
PGA2: medium gain and offset tuning
PGA3: fine gain and offset tuning
V
D
1
=
(Eq. 5)
GD
1
⋅
V
October 2008
IN
Table 42. Analog input reference selection
(RegACCfg5[0])
Table 43. PGA and ADC enabling
Enable [3:0]
VMUX
XXX0
XXX1
XX0X
XX1X
X0XX
X1XX
0XXX
1XXX
0
1
V [ ]
Page 58
AC_R(1)
AC_R(3)
V
REFP
PGA1 disabled
PGA2 disabled
PGA3 disabled
PGA1 enabled
PGA2 enabled
PGA3 enabled
ADC disabled
ADC enabled
Block
High gain acquisition for sensor interface
AC_R(0)
AC_R(2)
V
REFN
DATASHEET
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SX8722
D1
at the output of