ZHCS898O October 2003 – March 2019 TMS320F2801 , TMS320F28015 , TMS320F28016 , TMS320F2802 , TMS320F2806 , TMS320F2808 , TMS320F2809
PRODUCTION DATA.
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A simplified functional block diagram of the ADC module is shown in Figure 6-7. 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:
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. Figure 6-7 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.
To obtain the specified accuracy of the ADC, proper board layout is very critical. To the best extent possible, traces leading to the ADCIN pins should not run in close proximity to the digital signal paths. This is to minimize switching noise on the digital lines from getting coupled to the ADC inputs. Furthermore, proper isolation techniques must be used to isolate the ADC module power pins (VDD1A18, VDD2A18, VDDA2, VDDAIO) from the digital supply. Figure 6-8 and Figure 6-9 show the ADC pin connections for the 280x devices.
NOTE
Figure 6-8 shows the ADC pin-biasing for internal reference and Figure 6-9 shows the ADC pin-biasing for external reference.
NOTE
The temperature rating of any recommended component must match the rating of the end product.