SPRSP45B March 2020 – December 2020 TMS320F280021 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C-Q1
Figure 7-35 shows the ADC conversion timings for two SOCs given the following assumptions:
Table 7-12 lists the descriptions of the ADC timing parameters. Table 7-13 lists the ADC timings.
|tSH||The duration of the S+H window.
At the end of this window, the value on the S+H capacitor becomes the voltage to be converted into a digital value. The duration is given by (ACQPS + 1) SYSCLK cycles. ACQPS can be configured individually for each SOC, so tSH will not necessarily be the same for different SOCs.
Note: The value on the S+H capacitor will be captured approximately 5 ns before the end of the S+H window regardless of device clock settings.
|tLAT||The time from the end of the S+H window until the ADC results latch in the ADCRESULTx register.
If the ADCRESULTx register is read before this time, the previous conversion results will be returned.
|tEOC||The time from the end of the S+H window until the S+H window for the next ADC conversion can begin. The subsequent sample can start before the conversion results are latched.|
|tINT||The time from the end of the S+H window until an ADCINT flag is set (if configured).
If the INTPULSEPOS bit in the ADCCTL1 register is set, tINT will coincide with the conversion results being latched into the result register.
If the INTPULSEPOS bit is 0, tINT will coincide with the end of the S+H window. If tINT triggers a read of the ADC result register (directly through DMA or indirectly by triggering an ISR that reads the result), care must be taken to ensure the read occurs after the results latch (otherwise, the previous results will be read).
If the INTPULSEPOS bit is 0, and the OFFSET field in the ADCINTCYCLE register is not 0, then there will be a delay of OFFSET SYSCLK cycles before the ADCINT flag is set. This delay can be used to enter the ISR or trigger the DMA at exactly the time the sample is ready.
|ADCCLK PRESCALE||SYSCLK CYCLES||ADCCLK CYCLES|
|ADCCTL2 [PRESCALE]||RATIO ADCCLK:SYSCLK||tEOC||tLAT(1)||tINT(EARLY)(2)||tINT(LATE)||tEOC|