XE8000EV120 Semtech, XE8000EV120 Datasheet - Page 72

• Manufacturer Part Number: XE8000EV120
• Description: BOARD EVAL FOR SX8722I070TRLF
• Manufacturer: Semtech
• Series: ZoomingADC™r

Specifications of XE8000EV120

• Number Of Adc's: 1
• Number Of Bits: 16
• Data Interface: I²C
• Inputs Per Adc: 7 Single or 4 Differential
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 125°C
• Utilized Ic / Part: SX8722
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: XM8000EV120; XM8000EV120

Finally, remember that power reduction is typically traded off with reduced linearity, larger noise and slower maximum
sampling speed.
12.15. Noise
Ideally, a constant input voltage V
code may vary for a fixed input voltage. Thus, a statistical analysis on the output code of 1200 conversions for a constant
input voltage was performed to derive the equivalent noise levels of PGA1, PGA2, and PGA3. The extracted rms output
noise of PGA1, 2, and 3 are given in Table 58: standard output deviation and output rms noise voltage. Figure 37 shows the
distribution for the ADC alone (PGA1, 2, and 3 bypassed). Quantization noise is dominant in this case, and, thus, the ADC
thermal noise is below 16 bits.
The simple noise model of Figure 38 is used to estimate the equivalent input referred rms noise V
in the model of Figure 39. This is given by the relationship:
where V
3 respectively. As shown in this equation, noise can be reduced by increasing OSR and N
averaging effect, but reduces noise).
ACS - Revision 4.2
©2008 Semtech Corp.
ADVANCED COMMUNICATIONS & SENSING
V
N
,
IN
2
N1
=
, V
⎛
⎜ ⎜
⎝
GD
N2
V
Table 58. PGA Noise Measurements (n = 16 bits, OSR = 512, N
N
, and V
1
1
⎞
⎟ ⎟
⎠
2
Figure 37. ADC Noise (PGA1, 2 & 3 Bypassed, OSR = 512, N
+
N3
⎛
⎜ ⎜
⎝
GD
Standard deviation at ADC output (LSB)
are the output rms noise figures of Table 58, GD1, GD2, and GD3 are the PGA gains of stages 1 to
V
1
(
(Eq. 24)
OSR
N
⋅
GD
2
Output RMS noise(uV)
October 2008
2
⋅
IN
N
⎞
⎟ ⎟
⎠
2
should result in a constant output code. However, because of circuit noise, the output
ELCONV
Parameter
+
⎛
⎜ ⎜
⎝
GD
80
60
40
20
0
)
-5
1
⋅
GD
V
-4
Output Code Deviation From Mean Value [LSB]
N
3
2
⋅
-3
GD
-2
3
Page 72
⎞
⎟ ⎟
⎠
2
-1
205 x (V
0
PGA1
0.85
1
High gain acquisition for sensor interface
N1
[
2
)
V
3
340 x (V
2
rms
PGA2
4
1.4
ELCONV
5
]
N2
)
365 x (V
ELCONV
PGA3
= 2, V
1.5
ELCONV
N,IN
N3
= 2)
REF
)
of the acquisition chain
DATASHEET
(increases the ADC
= 5 V)
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SX8722