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2014-07-02 - Gecko Family - d0001_Rev1.30
377
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Figure 25.3. ADC Analog Power Consumption With Different WARMUPMODE Settings
ADC enabled
Conversion t rigger
Conversion t rigger
Power
Power
Power
Tim e
Tim e
ADC warm - up
ADC conversion
Bandgap reference warm - up
5 µs
1 µs
1 µs
5 µs
5 µs
5 µs
NORMAL
KEEPSCANREFWARM
(w SCANREF = internal bandgap)
KEEPADCWARM
(w SCANREF = internal bandgap)
Power
Tim e
FASTBG
(w SCANREF = any)
or
NORMAL
(w SCANREF = external or VDD)
a)
b)
c)
d)
25.3.4 Input Selection
The ADC is connected to 8 external input pins, which can be selected as 8 different single ended inputs or
4 differential inputs. In addition, 6 single ended internal inputs can be selected. The available selections
are given in the register description for ADCn_SINGLECTRL and ADCn_SCANCTRL.
For offset calibration purposes it is possible to internally short the differential ADC inputs and thereby
measure a 0 V differential. Differential 0 V is selected by writing the DIFF bit to 1 and INPUTSEL to 4 in
ADCn_SINGLECTRL. Calibration is described in detail in Section 25.3.10 (p. 382) .
Note
When VDD/3 is sampled, the acquisition time should be above a lower limit. The reader is
referred to the datasheet for minimum VDD/3 acquisition time.
25.3.4.1 Input Filtering
The selected input signal can be filtered, either through an internal low pass RC filter or an internal
decoupling capacitor. The different filter configurations can be enabled through the LPFMODE bits in
ADCn_CTRL. For maximum SNR, LPFMODE is recommended set to DECAP, with a cutoff frequency
of 31.5 MHz.
The RC input filter configuration is given in Figure 25.4 (p. 378) . The resistance and capacitance values
are given in the electrical characteristics for the device, named R
ADCFILT
and C
ADCFILT
respectively.
Summary of Contents for EFM32G
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