ADS124S06: if channels switching during each conversion required then How to use ADS124S06 ?

Hi Vijendra,

See my responses below.

Best regards,

Bob B

Vijendra Goyal said:

Part Number: ADS124S06

Hello Team,

We are using 4 analog channels to measure 2 differential signals as:

AIN0, AIN1 for one differential signal measurement and AIN4, AIN5 for second differential signal measurement. Global chop mode is Off in both the cases.

During both cases we have below setting in data rate register

 Data Rate Register          0x11 [Bob] This is global chop disabled, internal oscillator, continuous conversion mode, low-latency filter, and 5sps.

We are switching channels during measurements. So we have below issues:-

1.How much minimum delay required to provide actual results in conversion during channel switching? [Bob] There is no standard answer here because the required delay is highly dependent on any analog settling.  If both differential inputs are stable, then I would suggest using the Programmable Conversion Delay at the default setting of 14 tmod periods.  Using the internal oscillator this will be approximately 55us.  The first conversion using the low-latency filter at 5sps will be 206.504ms (Table 13 of the ADS124S06 datasheet) after the mux change and programmable delay period.  So after the register write when changing the mux the time will be a minimum of the programmable conversion delay (55us) + first conversion (206.504ms) for a minimum time of 206.559ms before the conversion result is ready to be read out of the ADS124S06.

2.We are sending start command to ADC after every channel switching. [Bob] This is not actually doing anything when in continuous conversion mode.  Sending the Start command would be required if in single-shot mode.  If you want to restart a conversion while in continuous conversion mode you must first send the Stop command followed by the Start command.  However this would be unnecessary as the conversion will restart automatically when the mux register is changed.

3.We are using Continuous conversion mode as Data_rate_resister settings is 0x11. Should we change it in single shot conversion mode? [Bob] The only reasons for you to change to single-shot mode is if you have no way of keeping track of when the conversion result is ready to be read from the device other than by time, or you are polling DRDY put there could be a possibility of missing the DRDY transition and a new conversion would start.  Normally when cycling the mux you would monitor DRDY and as soon as DRDY transitions from a high to low state you would change to the next mux setting at the same time as reading the conversion result.  This will give you the fastest cycle time between the two input channels with minimum delays.

Thanks & Regards

Vijendra