LM3S9B81 Datasheet, PDF (496/1155 Pages) Texas Instruments – Stellaris® LM3S9B81 Microcontroller

Analog-to-Digital Converter (ADC)
13
Analog-to-Digital Converter (ADC)
An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a
discrete digital number. Two identical converter units are included, which share sixteen input channels.
The Stellaris^® ADC module features 10-bit conversion resolution and supports sixteen input channels,
plus an internal temperature sensor. The ADC module contains four programmable sequencers
allowing the sampling of multiple analog input sources without controller intervention. Each sample
sequencer provides flexible programming with fully configurable input source, trigger events, interrupt
generation, and sequencer priority. A digital comparator function is included which allows the
conversion value to be diverted to a digital comparator module. The digital comparator module
provides 16 digital comparators. Each digital comparator evaluates the ADC conversion value
against its two user-defined values to determine the operational range of the signal. The trigger
source for ADC0 and ADC1 may be independent or the two ADC units may operate from the same
trigger source and operate on the same or different inputs. A phase shifter can delay the start of
sampling by a specified phase angle. When using both ADC modules, it is possible to configure the
converters to start the conversions coincidentally or within a relative phase from each other, see
“Sample Phase Control” on page 501.
The Stellaris^® LM3S9B81 microcontroller provides two ADC modules with the following features:
■ 16 analog input channels
■ Single-ended and differential-input configurations
■ On-chip internal temperature sensor
■ Maximum sample rate of one million samples/second
■ Optional phase shift in sample time programmable from 22.5º to 337.5º
■ Four programmable sample conversion sequencers from one to eight entries long, with
corresponding conversion result FIFOs
■ Flexible trigger control
– Controller (software)
– Timers
– Analog Comparators
– GPIO
■ Hardware averaging of up to 64 samples for improved accuracy
■ Digital comparison unit providing 16 digital comparators
■ Converter uses an internal 3-V reference or an external reference
■ Power and ground for the analog circuitry is separate from the digital power and ground
■ Efficient transfers using Micro Direct Memory Access Controller (µDMA)
– Dedicated channel for each sample sequencer
496
June 29, 2010
Texas Instruments-Advance Information