xe8802 Semtech Corporation, xe8802 Datasheet - Page 127

• Manufacturer Part Number: xe8802
• Description: Data Acquisition Soc With 16+10 Bit Zoomingadc? Embedded Risc Controller And Lcd Driver
• Manufacturer: Semtech Corporation

Recalling equation Eq. 9, this can be rewritten as:
where, from Eq. 10 and Eq. 11, the total PGA gain and offset are respectively:
and:
The equivalent LSB size at the input of the PGA chain is:
Notice that the input voltage V
© Semtech 2006
Table 17-25. Last forced LSBs in conversion output registers for resolution settings smaller than 16
OUT
GD
GDoff
LSB
SET_OSR
TOT
[2:0]
ADC
=
000
001
010
011
100
101
110
111
TOT
2
=
Table 17-24. Basic ADC Relationships (example for: V
1
n
=
GD
=
⋅
2
GD
GDoff
V
16
3
REF
⋅
⋅
TOT
GD
V
SET_NELC = 00
V
REF
IN
3
⋅
2
OSR
+
⋅
1000000000
⋅
GD
OSR
⎛
⎜ ⎜
⎝
GD
GD
10000000
ADC Input
+2.49505V
+2.49497V
+76.145µV
-76.145µV
-2.49505V
-2.49513V
IN,ADC
bits (n < 16) (RegAcOutMsb[7:0] & RegAcOutLsb[7:0])
Voltage
1
+
3
V
100000
1
TOT
⋅
IN,ADC
0V
GDoff
...
...
1000
of the ADC must satisfy the condition:
−
10
GDoff
-
-
-
2
(V/V)
(V)
SET_NELC = 01
+0.5⋅FS
-0.5⋅FS
XE8802 Sensing Machine Data Acquisition MCU
TOT
Scale
% of
(FS)
Full
...
...
...
...
...
...
0
100000000
⋅
V
(V/V)
V
1000000
REF
IN
10000
⎞
⎟ ⎟
⎠
100
⋅
Output in
=+32'767
=+32'766
17-15
=-32'767
=-32'768
OSR 1
1
-
-
-
+2
+2
LSBs
-2
OSR
-2
+1
-1
...
...
15
15
15
0
15
SET_NELC = 10
-1
-1
-2
+
with ZoomingADC™ and LCD driver
10000000
Output
in Hex
100000
Code
7FFF
7FFE
FFFF
0000
8001
8000
0001
...
...
1000
(LSB) (Eq. 18)
(Eq. 19)
10
REF
-
-
-
-
= 5V, OSR = 512, n = 16 bits)
SET_NELC = 11
1000000
10000
100
1
-
-
-
-
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