![](http://datasheet.mmic.net.cn/Semtech/XE8802MI035LF_datasheet_100001/XE8802MI035LF_128.png)
Semtech 2006
www.semtech.com
17-16
XE8802 Sensing Machine Data Acquisition MCU
with ZoomingADC and LCD driver
1
)
(
2
1
,
+
≤
OSR
V
REFN
REFP
ADC
IN
(V)
(Eq. 20)
to remain within the ADC input range.
17.7.8
Power Saving Modes
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 17-26). 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.
IB_AMP_ADC
[1:0]
IB_AMP_PGA
[1:0]
ADC
Bias
Current
PGA
Bias
Current
Max. fS
[kHz]
00
01
10
11
x
1/4
I
ADC
1/2
I
ADC
3/4
I
ADC
IADC
x
62.5
125
250
500
x
00
01
10
11
x
1/4
I
PGA
1/2
I
PGA
3/4
I
PGA
IPGA
62.5
125
250
500
Table 17-26. ADC & PGA power saving modes and maximum sampling frequency
17.8
Specifications and Measured Curves
This section presents measurement results for the acquisition chain. A summary table with circuit specifications
and measured curves are given.
17.8.1
Default Settings
Unless otherwise specified, the measurement conditions are the following:
Temperature TA = +25°C
VDD = +5V, GND = 0V, VREF = +5V, VIN = 0V
RC frequency fRC = 2MHz, sampling frequency fS = 500kHz
Offsets GDOff2 = GDOff3 = 0
Power operation: normal (IB_AMP_ADC[1:0] = IB_AMP_PGA[1:0] = '11')
Resolution:
for n = 12 bits: OSR = 32 and NELCONV = 4
o
for n = 16 bits: OSR = 512 and NELCONV = 2
Not
Recommended
for
New
Designs