TMS320F28335, TMS320F28334, TMS320F28332
TMS320F28235, TMS320F28234, TMS320F28232
SPRS439I–JUNE 2007–REVISED MARCH 2011
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4.7 Analog-to-Digital Converter (ADC) Module
A simplified functional block diagram of the ADC module is shown in Figure 4-8. 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 dedicated ADC channels. 8 channels multiplexed per Sample/Hold
Autosequencing capability provides up to 16 "autoconversions" in a single session. Each conversion
can be programmed to select any 1 of 16 input channels
•
•
Sequencer can be operated as two independent 8-state sequencers or as one large 16-state
sequencer (i.e., two cascaded 8-state sequencers)
Sixteen result registers (individually addressable) to store conversion values
–
The digital value of the input analog voltage is derived by:
Digital Value = 0,
when input £ 0 V
Input Analog Voltage - ADCLO
Digital Value = 4096 ´
when 0 V < input < 3 V
3
Digital Value = 4095,
when input ³ 3 V
•
Multiple triggers as sources for the start-of-conversion (SOC) sequence
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–
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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 2833x/2823x devices 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 16 channels, configurable as two independent
8-channel modules. The two independent 8-channel modules can be cascaded to form a 16-channel
module. Although there are multiple input channels and two sequencers, there is only one converter in the
ADC module. Figure 4-8 shows the block diagram of the ADC module.
The two 8-channel 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.
78
Peripherals
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