Texas Instruments TMS320F2802 User Manual
Page 62
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SPRS230N – OCTOBER 2003 – REVISED MAY 2012
4.6
Enhanced Analog-to-Digital Converter (ADC) Module
A simplified functional block diagram of the ADC module is shown in
. The ADC module
consists of a 12-bit ADC with a built-in sample-and-hold (S/H) circuit. Functions of the ADC module
include:
•
12-bit ADC core with built-in S/H
•
Analog input: 0.0 V to 3.0 V (Voltages above 3.0 V produce full-scale conversion results.)
•
Fast conversion rate: Up to 80 ns at 25-MHz ADC clock, 12.5 MSPS
•
16-channel, MUXed inputs
•
Autosequencing capability provides up to 16 "autoconversions" in a single session. Each conversion
can be programmed to select anyone of 16 input channels
•
Sequencer can be operated as two independent 8-channel sequencers or as one large 16-channel
sequencer (that is, two cascaded 8-channel sequencers)
•
Sixteen result registers (individually addressable) to store conversion values
–
The digital value of the input analog voltage is derived by:
A.
All fractional values are truncated.
•
Multiple triggers as sources for the start-of-conversion (SOC) sequence
–
S/W - software immediate start
–
ePWM start of conversion
–
XINT2 ADC start of conversion
•
Flexible interrupt control allows interrupt request on every end-of-sequence (EOS) or every other EOS.
•
Sequencer can operate in "start/stop" mode, allowing multiple "time-sequenced triggers" to
synchronize conversions.
•
SOCA and SOCB triggers can operate independently in dual-sequencer mode.
•
Sample-and-hold (S/H) acquisition time window has separate prescale control.
The ADC module in the 280x has been enhanced to provide flexible interface to ePWM peripherals. The
ADC interface is built around a fast, 12-bit ADC module with a fast conversion rate of up to 80 ns at 25-
MHz ADC clock. The ADC module has a 16-channel sequencer, configurable as two independent 8-
channel sequencers. The two independent 8-channel sequencers can be cascaded to form a 16-channel
sequencer. Although there are multiple input channels and two sequencers, there is only one converter in
the ADC module.
shows the block diagram of the ADC module.
The two 8-channel sequencer modules have the capability to autosequence a series of conversions, each
module has the choice of selecting any one of the respective eight channels available through an analog
MUX. In the cascaded mode, the autosequencer functions as a single 16-channel sequencer. On each
sequencer, once the conversion is complete, the selected channel value is stored in its respective
RESULT register. Autosequencing allows the system to convert the same channel multiple times, allowing
the user to perform oversampling algorithms. This gives increased resolution over traditional single-
sampled conversion results.
62
Peripherals
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