8.10.2 External Reference Voltage
To convert the voltage presented as a ratiometric signal, the external VREFHI/VREFLO pins should be chosen
to generate the reference voltage. In contrast with the fixed 0 to 3.3 V input range of the internal bandgap mode,
the ratiometric mode has an input range from VREFLO to VREFHI. Converted values will scale to this range.
For instance, if VREFLO is set to 0.5 V and VREFHI is 3.0 V, a voltage of 1.75 V will be converted to the digital
result of 2048. See the device data sheet for the allowable ranges of VREFLO and VREFHI. On some devices
VREFLO is tied to ground internally, and hence limited to 0 V. The equation governing the conversions in this
mode is:
Digital Value = 0
when Input ≤ VREFLO
Digital Value = 4096 [(Input – VREFLO)/(VREFHI – VREFLO)]
when VREFLO < Input < VREFHI
Digital Value = 4095,
when Input ≥ VREFHI
*All fractional values are truncated
8.11 ADC Timings
SOC0
ADCCLK
ADCRESULT 0
S/H Window Pulse to Core
ADCCTL 1.INTPULSEPOS
ADCSOCFLG 1.SOC0
ADCINTFLG .ADCINTx
SOC1
SOC2
9
15
22
24
37
2
0
Result 0 Latched
ADCSOCFLG 1.SOC1
ADCSOCFLG 1.SOC2
ADCRESULT 1
EOC0 Pulse
EOC1 Pulse
Conversion 0
13 ADC Clocks
Minimum
7 ADCCLKs
6
ADCCLKs
Conversion 1
13 ADC Clocks
Minimum
7 ADCCLKs
2 ADCCLKs
1 ADCCLK
Analog Input
SOC1 Sample
Window
SOC0 Sample
Window
SOC2 Sample
Window
Figure 8-8. Timing Example For Sequential Mode / Late Interrupt Pulse
Analog-to-Digital Converter (ADC)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
527
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
Страница 2: ......