ZHCSMK4A september 2022 – july 2023 ADS131B26-Q1
PRODUCTION DATA
In continuous-conversion mode, ADC1y and ADC3y convert indefinitely until stopped by the host. Set the respective STARTy bits in the CONVERSION_CTRL register to start conversions of the enabled ADCs, ADC1y and ADC3y. ADC1A and ADC3A start converting simultaneously when the STARTA bit is set. The same is true for ADC1B and ADC3B and the STARTB bit. However, conversions on ADCxA and ADCxB can be started at different times using the respective STARTA and STARTB bits. Setting the STARTy bit while conversions are ongoing on an ADC aborts the ongoing conversion and restarts conversions. Use the STOPy bits to stop conversions of the enabled ADCs, ADC1y and ADC3y. The currently ongoing conversion is allowed to finish after the STOPy bit is set and the digital filter is held in reset thereafter. After setting the STOPy bits, the STOPy bits read back 1b until conversions are stopped.
The STARTy bits take priority over the STOPy bits. That means if both the STARTy and STOPy bits in the CONVERSION_CTRL register are set at the same time, then conversions are started or ongoing conversions are aborted and new conversions are started.
The last conversion result of an ADC is still available for readout after conversions are stopped. The conversion results of an ADC are only cleared after a device reset, when the ADC is disabled, when the device is in standby or power-down mode, or are overwritten when a new conversion result becomes available.
The STARTy bits take effect and conversions start at the last SCLK falling edge of the register data CRC word within the SPI frame where the CONVERSION_CTRL register is written. See the Serial Interface Communication StructureSerial InterfaceSerial Interface SignalsSerial Interface Communication Structure section for details on the SPI frame of a register write command.
Setting the STARTy bit drives the DRDYn pin high if DRDYn was low, however the old conversion data can still be read until the new conversions become available.
ADC1y and ADC3y use a sinc3 digital filter that requires three conversion periods to settle. When conversions are started or restarted using the STARTy bits, the device hides the first two unsettled conversions and only provides a settled conversion result after the third conversion period. Use Equation 19 to calculate the time until the first conversion after a conversion start is available. All subsequent conversions have a conversion period, as shown in Figure 9-17, of tDATA = 1 / fDATA = OSR / fMOD.
The ADC does not detect when a sudden step change on the analog input occurs while the ADC is continuously converting. Therefore, the ADC continues to output conversion data at the programmed output data rate. If the step change occurs concurrently with the start of a new conversion period, then settled data are output three conversion periods after the step change. However, the sinc3 filter takes four conversion periods to provide settled data, as shown in Figure 9-18, if the step change occurs in the middle of a conversion period.