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EFM32WG Datasheet, PDF (682/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.
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Figure 28.1. ADC Overview
...the world's most energy friendly microcontrollers
AD Cn _STATUS
AD Cn _CTRL
AD Cn _CMD
AD Cn _SINGLECTRL
AD Cn _SCANCTRL
AD Cn _SINGLED ATA
AD Cn _SCAND ATA
Oversam pling
filter
HFPERCLKADCn
Prescaler ADC_CLK
AD Cn _CH0
AD Cn _CH1
AD Cn _CH2
AD Cn _CH3
AD Cn _CH4
AD Cn _CH5
AD Cn _CH6
AD Cn _CH7
Tem p
VDD/3
VDD
VSS
Vref/2
D AC0 / OPA0
D AC1 / OPA1
Se q u e n c e r
Cont rol
+
SAR
-
Re su l t
buffer
VDD
1.25 V
2.5 V
5 V differential
2 x ( VD D -VSS)
28.3.1 Clock Selection
The ADC has an internal prescaler (PRESC bits in ADCn_CTRL) which can divide the peripheral clock
(HFPERCLK) by any factor between 1 and 128. Note that the resulting ADC_CLK should not be set to
a higher frequency than 13 MHz and not lower than 32 kHz.
28.3.2 Conversions
A conversion consists of two phases. The input is sampled in the acquisition phase before it is converted
to digital representation during the approximation phase. The acquisition time can be configured
independently for scan and single conversions (see Section 28.3.7 (p. 686) ) by setting AT in
ADCn_SINGLECTRL/ADCn_SCANCTRL. The acquisition times can be set to any integer power of 2
from 1 to 256 ADC_CLK cycles.
Note
For high impedance sources the acquisition time should be adjusted to allow enough time
for the internal sample capacitor to fully charge. The minimum acquisition time for the
internal temperature sensor and Vdd/3 is given in the electrical characteristics for the device.
The analog to digital converter core uses one clock cycle per output bit in the approximation phase.
ADC Total Conversion Time (in ADC_CLK cycles) Per Output
Tconv= (TA+N) x OSR
(28.1)
TA equals the number of acquisition cycles and N is the resolution. OSR is the oversampling ratio (see
Section 28.3.7.7 (p. 688) ). The minimum conversion time is 7 ADC_CYCLES with 6 bit resolution and
13 ADC_CYCLES with 12 bit resolution. The maximum conversion time is 1097728 ADC_CYCLES with
the longest acquisition time, 12 bit resolution and highest oversampling rate.
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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