ADC Special Modes
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SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Analog To Digital Converter (ADC) Module
19.8.3 ADC Power-Down Mode
This is an inactive mode in which the clocks to the ADC module are stopped leaving the module in a static
state. The clock to the ADC core (ADCLK) is stopped whenever there are no ongoing conversions. This is
the clock-gating implementation requirement. Also, the ADC module places the ADC core into the power
down mode such that there is minimal current drawn from the ADC operating and reference supplies.
19.8.3.1 Powering Down Just The ADC Core
The ADC core can be individually powered down without stopping the clocks to the ADC module. This can
be done by setting the POWERDOWN bit of the ADC Operating Mode Control Register
(ADOPMODECR.3). Whenever a conversion is required the POWERDOWN bit must be cleared, and a
minimum time
t
d(PU-ADV)
,
(see the specific device data sheet for actual value) has to be allowed before
starting a new conversion. This wait must be implemented in the application software.
19.8.3.2 Enhanced Power-Down Mode
A bit in the ADC operating mode control register, IDLE_PWRDN (ADOPMODECR.4) enables the
enhanced power-down mode of the ADC.
Once this bit is set, the ADC module will power down the ADC core whenever there are no more ongoing
or pending ADC conversions. The ADC core will be powered down regardless of the state of the
POWERDOWN bit (ADOPMODECR.3).
The ADC module releases the ADC core from power down mode as soon as a new conversion is
requested. The ADC logic state machine then has to wait for at least
t
d(PU-ADV)
(see the device data sheet
for actual value) before starting a new conversion. The IDLE_PWRDN bit will remain set at all times. The
logic state machine can use this bit to determine that it needs to wait for a programmable number of VCLK
cycles before it allows the input channel to be sampled. This time is configured by the ADC Power Up
Delay Control register (ADPWRUPDLYCTRL).
If IDLE_PWRDN is not set, the ADC module does not wait for any additional delay before sampling the
input channel and the application software has to take account of this required delay.
19.8.3.3 Managing Clocks to the ADC Module
The clock to the ADC module can be turned off via the appropriate Peripheral Central Resource (PCR)
controller PSPWRDNSET register (check the specific device datasheet to identify the register and the bit
to be set). If a conversion is ongoing when this bit is set, the ADC module will wait until the current
conversion completes before allowing the ADC module clock to be stopped.
