xe88lc05 ETC-unknow, xe88lc05 Datasheet - Page 27

• Manufacturer Part Number: xe88lc05
• Description: 16 10 Bit Data Acquisition Ultra Low-power Microcontroller
• Manufacturer: ETC-unknow

Table 8.6:
Table 8.7:
8.10 Noise
Figure 8.16:
27
-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
2
100
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
10
20
1
5
n in
TOT
IN
,
[mV]
=
15


----------------------------------------------------------------------------------------------------------------------------------------------- -
V
-----------------
gain1
n out1
,
PGA1 Gain
20
(V/V)
GD1


10
10
10
10
1
1
2
Data Acquisition Microcontroller
+
25


--------------------------------- -
gain1 gain2
V
n out2
,
PGA2 Gain
numconv smax
⋅
bypassed
bypassed
IN
(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


2
IN
[mV]
XE88LC05
15
20
D0109-40
25