![](http://datasheet.mmic.net.cn/Semtech/XE8805AMI028LF_datasheet_100002/XE8805AMI028LF_103.png)
Semtech 2006
www.semtech.com
16-17
XE8805/05A
=
IN
REF
TOT
REF
IN
ADC
V
GDoff
GD
V
OUT
16
2
OSR
OSR 1
+
(LSB)
(Eq. 18)
where, from Eq. 10 and Eq. 11, the total PGA gain and offset are respectively:
1
2
3
GD
TOT
=
(V/V)
and:
2
3
GDoff
GD
GDoff
TOT
+
=
(V/V)
ADC Input
Voltage
VIN,ADC
% of
Full
Scale
(FS)
Output in
LSBs
Output
Code
in Hex
+2.49505V
+0.5
FS
+2
15-1
=+32'767
7FFF
+2.49497V
...
+2
15-2
=+32'766
7FFE
...
+76.145
V
...
+1
0001
0V
0
0000
-76.145
V
...
-1
FFFF
...
-2.49505V
...
-2
15-1
=-32'767
8001
-2.49513V
-0.5
FS
-2
15
=-32'768
8000
Table 16-24. Basic ADC Relationships (example for: VREF = 5V, OSR = 512, n = 16 bits)
SET_OSR
[2:0]
SET_NELC = 00
SET_NELC = 01
SET_NELC = 10
SET_NELC = 11
000
1000000000
100000000
10000000
1000000
001
10000000
1000000
100000
10000
010
100000
10000
1000
100
011
1000
100
10
1
100
10
1
-
101
-
110
-
111
-
Table 16-25. Last forced LSBs in conversion output registers for resolution settings smaller than 16
bits (n < 16) (RegAcOutMsb[7:0] & RegAcOutLsb[7:0])
Not
Recommended
for
New
Designs