XE8805 SEMTECH [Semtech Corporation], XE8805 Datasheet - Page 104

• Manufacturer Part Number: XE8805
• Description: Data Acquisition MCU
• Manufacturer: SEMTECH [Semtech Corporation]

The equivalent LSB size at the input of the PGA chain is:
Notice that the input voltage V
to remain within the ADC input range.
16.7.8
During low-speed operation, the bias current in the PGAs and ADC can be programmed to save power using the
control words IB_AMP_PGA[1:0] and IB_AMP_ADC[1:0] (see Table 16-26). If the system is idle, the PGAs and
ADC can even be disabled, thus, reducing power consumption to its minimum. This can considerably improve
battery lifetime.
16.8 Specifications and Measured Curves
This section presents measurement results for the acquisition chain. A summary table with circuit specifications
and measured curves are given.
© Semtech 2006
LSB
V
IN
Power Saving Modes
,
ADC
=
2
1
≤
n
Table 16-26. ADC & PGA power saving modes and maximum sampling frequency
⋅
1
2
GD
V
⋅
(
REF
V
TOT
REFP
IB_AMP_ADC
⋅
OSR
[1:0]
−
OSR
V
00
01
10
11
x
REFN
IN,ADC
+
1
)
⋅
OSR
of the ADC must satisfy the condition:
OSR
IB_AMP_PGA
(V)
+
[1:0]
1
00
01
10
11
x
(V)
Current
1/4⋅I
1/2⋅I
3/4⋅I
ADC
Bias
I
ADC
16-18
x
ADC
ADC
ADC
1/4⋅I
1/2⋅I
3/4⋅I
Current
PGA
Bias
I
PGA
x
PGA
PGA
PGA
Max. f
(Eq. 19)
(Eq. 20)
[kHz]
62.5
62.5
125
250
500
125
250
500
S
XE8805/05A
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