sx8725c Semtech Corporation, sx8725c Datasheet - Page 23

• Manufacturer Part Number: sx8725c
• Description: Zoomingadc For Sensing Data Acquisition
• Manufacturer: Semtech Corporation

Revision 1.01
© Semtech
7.5 Second Stage Programmable Gain Amplifier (PGA2)
The second PGA has a finer gain and offset tuning capability, as shown in
PGA2 is given by:
where GD
Pga2Gain[1:0] and Pga2Offset[3:0].
7.6 Third Stage Programmable Gain Amplifier (PGA3)
The finest gain and offset tuning is performed with the third and last PGA stage, according to the coding of
ADVANCED COMMUNICATIONS & SENSING
2
and GD
OFF2
Pga2Gain bitfield
Pga3Gain bitfield
(RegACCfg2[5:4])
(RegACCfg3[6:0])
are respectively the gain and offset of PGA2 (in V/V). These are controlled with the words
0000000
0000001
0000110
0001100
0010000
0100000
January 2011
00
01
10
11
...
...
...
Table 13. PGA3 Gain and Offset Settings
V
Table 12. PGA2 gain and offset settings
D
PGA2 gain [V/V]
2
1/12 (=0.083)
PGA3 Gain
GD
GD
=
12/12
16/12
32/12
GD
6/12
2
3
10
...
...
...
1
2
5
0
[V/V]
[V/V]
2
⋅
V
D
Page 23
Equation 6
1
−
GDoff
Pga2Offset bitfield
Pga3Offset bitfield
2
(RegACCfg2[3:0])
(RegACCfg4[6:0])
⋅
ZoomingADC for sensing data acquisition
S
0000000
0000001
0010000
0100000
0111111
1000000
⋅
V
0000
0001
0010
0011
0100
0101
1000
1001
1010
1011
1100
1101
...
...
...
REF
Table
[
V
]
12. The V
+63/12 (=+5.25)
+1/12 (=0.083)
GD
GD
PGA3 Offset
PGA2 offset
+16/12
OFF3
OFF2
32/12
www.semtech.com/products/
+0.2
+0.4
+0.6
+0.8
-0.2
-0.4
-0.6
-0.8
-1.0
D2
+1
0
0
0
...
...
0
[V/V]
[V/V]
voltage at the output of
SX8725C
DATASHEET
Table
13.