Convert Start
ADTM = 1
ADEN = 0
Powered
Down
Powered
Down
T
4
C
Power-Up
and Track
T
C T
C T
C
Power-Up
and Track
T C..
ADTM = 0
ADEN = 0
Powered
Down
Powered
Down
C
Power-Up
and Track
T C T C T C
Power-Up
and Track
T C..
ADPWR
T = Tracking set by ADTK
T4 = Tracking set by ADTM (4 SAR clocks)
C = Converting
ADTK
T
4
T
4
T
4
12.3.7 Burst Mode
Burst mode is a power saving feature that allows the ADC to remain in a low power state between conversions. When burst mode is
enabled, the ADC wakes from a low power state, accumulates 1, 4, 8, 16, 32, or 64 samples using the internal low-power high-frequen-
cy oscillator, then re-enters a low power state. Since the burst mode clock is independent of the system clock, the ADC can perform
multiple conversions then enter a low power state within a single system clock cycle, even if the system clock is running from a slow
oscillator.
Note:
When using burst mode, care must be taken to issue a convert start signal no faster than once every four SYSCLK periods. This
includes external convert start signals. The ADC will ignore convert start signals which arrive before a burst is finished.
Burst mode is enabled by setting ADBMEN to logic 1. When in burst mode, ADEN controls the ADC idle power state (i.e., the state the
ADC enters when not tracking or performing conversions). If ADEN is set to logic 0, the ADC is powered down after each burst. If AD-
EN is set to logic 1, the ADC remains enabled after each burst. On each convert start signal, the ADC is awakened from its idle power
state. If the ADC is powered down, it will automatically power up and wait for the amount of time programmed to the ADPWR bits be-
fore performing a conversion. Otherwise, the ADC will start tracking and converting immediately.
When burst mode is enabled, a single convert start will initiate a number of conversions equal to the repeat count. When burst mode is
disabled, a convert start is required to initiate each conversion. In both modes, the ADC end of conversion interrupt flag (ADINT) will be
set after “repeat count” conversions have been accumulated. Similarly, the window comparator will not compare the result to the great-
er-than and less-than registers until “repeat count” conversions have been accumulated.
12.3.8 8-Bit Mode
Setting the AD8BE bit to 1 will put the ADC in 8-bit mode. In 8-bit mode, only the 8 MSBs of data are converted, allowing the conversion
to be completed in fewer SAR clock cycles than a 10-bit conversion. The two LSBs of a conversion are always 00 in this mode, and the
ADC0L register will always read back 0x00.
EFM8UB3 Reference Manual
Analog-to-Digital Converter (ADC0)
silabs.com
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