XE88LC01MI000 ETC1 [List of Unclassifed Manufacturers], XE88LC01MI000 Datasheet - Page 28

• Manufacturer Part Number: XE88LC01MI000
• Description: Sensing Machine 16 + 10 bit Data Acquisition Ultra Low-Power Microcontroller
• Manufacturer: ETC1 [List of Unclassifed Manufacturers]

Table 8.6:
Table 8.7:
8.10 Noise
28
Figure 8.16:
-20
-40
-60
-80
80
60
40
20
0
0
16 bits - ADC converter (GDtot = 1000) (version v5a)
Vbat = Vref = 5.0V; fs = 500kHz; OSR = 512; NELCONV = 2
5
f
N sweep = 1201; average on 4 samples
RC
The gain settings of each PGA stage for the plots of above figure are those of the table below.
Individual PGA gains for INL & DNL measurements
Ideally, a constant input voltage V
of circuit noise, the output code may vary for a fixed input voltage. The figure shows the distri-
bution for the ADC alone (PGA1, 2, and 3 bypassed) and of several configurations of the
PGAs. Quantization noise is dominant in this case of ADC only, and, thus, the ADC thermal
noise is negligible.
One has to considere two points when computing final noise of the acquisition chain:
•
•
Total input refered noise can be computed using the following equation:
GAIN=1000, 16 bit ADC setting
= 2MHz; IB_AMP(1:0) = 11; Vinn=0V
PGA Gain
GD
V
10
10*V
(V/V)
1000
this is a type of amplifier (switched-cap with constant capacitive load) that maintains its output
noise when changing the gain. Therefore input refered noise is lowered when the gain of an
amplifier is increased.
the ADC is oversampled, and the number of samples taken lowers the thermal noise
2
100
10
20
1
5
n in
TOT
,
IN
[mV]
=
15


----------------------------------------------------------------------------------------------------------------------------------------------- -
V
-----------------
gain1
n out1
,
20
PGA1 Gain
(V/V)
GD1


10
10
10
10
1
1
2
+
25


--------------------------------- -
gain1 gain2
V
n out2
,
numconv smax
PGA2 Gain
⋅
IN
bypassed
bypassed
(V/V)
GD2
should result in a constant output code. However, because
10
10
5
2


2
⋅
+


----------------------------------------------------- -
gain1 gain2 gain3
PGA3 Gain
bypassed
bypassed
bypassed
bypassed
bypassed
-0.5
-1.0
-1.5
-2.0
2.0
1.5
1.0
0.5
0.0
(V/V)
GD3
10
⋅
V
0
16 bits - ADC converter (GDtot = 1000) (version v5a)
n out3
,
Vbat = Vref = 5.0V; fs = 500kHz; OSR = 512; NELCONV = 2
5
⋅
f
N sweep = 1201; average on 4 samples
RC
= 2MHz; IB_AMP(1:0) = 11; Vinn=0V
10
10*V


Data Sheet XE88LC01
Data Acquisition Microcontroller
2
IN
[mV]
15
20
D0202-60
25