Semtech 2005
www.semtech.com
16-10
XE8801A – SX8801R
PGA3_GAIN[6:0]
PGA3 Gain
GD3 (V/V)
0000000
0
0000001
1/12(=0.083)
...
0000110
6/12
...
0001100
12/12
0010000
16/12
...
0100000
32/12
...
1000000
64/12
...
1111111
127/12(=10.58)
Table 16-17 PGA3 gain settings
PGA3_OFFSET[6:0]
PGA3 Offset
GDoff3 (V/V)
0000000
0
0000001
+1/12(=+0.083)
0000010
+2/12
...
0010000
+16/12
...
0100000
+32/12
...
0111111
+63/12(=+5.25)
1000000
0
1000001
-1/12(=-0.083)
1000010
-2/12
...
1010000
-16/12
...
1100000
-32/12
...
1111111
-63/12(=-5.25)
Table 16-18 PGA3 offset settings
16.6.1
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 16-13. To reduce power dissipation, the ADC can also be inactivated
while idle.
16.6.2
PGA1
The first stage can have a buffer function (unity gain) or provide a gain of 10 (see Table 16-14). The voltage VD1 at
the output of PGA1 is:
IN
D
V
GD
V
=
1
(V)
(Eq. 5)
where GD1 is the gain of PGA1 (in V/V) controlled with the bit PGA1_GAIN.
Not
Recommended
for
New
Designs