ADS1261: SINC4

Hi Kai,

Kai Hsiao said:

May I know TI have SINC4 document to explain the detail ? 

Are you asking about the different types of SINC digital filters? If so, that a look at this blog post: https://e2e.ti.com/blogs_/archives/b/precisionhub/archive/2016/06/10/delta-sigma-adc-digital-filter-types-sinc-filters 

Between SINC1/2/3/4 digital filters, the main trade-off is the frequency repose vs settling time.

Kai Hsiao said:

May I know what's the key different between ADS1261 and ADS124S08 

What's the application prefer to use ADS1261 and what's the application prefer to use ADS124S08 ?

Some other significant differences between these devices are:

• The ADS1261 offers much faster data rates and has lower noise (better effective resolution).
• The ADS124S08 is a lower power device with faster digital filter settling.

With the faster data rates of the ADS1261, it is likely to be used in applications that benefit from the faster data rates such as when you need to MUX through multiple input channels quickly, or if your signal has some higher frequency content that you need to sample. Also with the AC bridge excitation signals built into the ADS1261, it is a good fit in very high precision weigh-scales.

Kai Hsiao said:

Anther solution's AD7124 ,so we would like to know which solution is better than AD7124?

This ADI device is quite similar to both of the above devices. I would probably recommend the ADS1261 as a replacement to this ADI device because it have better noise performance and faster data rates.

Best regards,
Chris

Hi Kai,

Kai Hsiao said:

You mean ADS124S08 have lower power and faster digital filter settling ,could you explain more detail ?

Power dissipation
Comparing the electrical specifications, you'll find that the ADS124S08 is a much lower power device; when active it consumes about 1.75 mW. The ADS1261's power dissipation is closer to 25mW.

Digital filter settling time
Take a look at Tables 13 &15 in the ADS124S08 datasheet and compare it to Table 17 in the ADS1261 datasheet. The first conversion result is a bit slower than the data rate due to the digital filter settling time and some additional delays (for example, the time to calculate the calibrated result). Overall, I guess the ADS124S08's low-latency filter is not all that different from the ADS1261's SINC1 filter. After taking a closer look at this I would probably revise my earlier statement and say that the ADS1261 offers more filtering options than the ADS124S08.

For additional details on digital filters please refer to this blog post:
https://e2e.ti.com/blogs_/archives/b/precisionhub/archive/2016/06/10/delta-sigma-adc-digital-filter-types-sinc-filters

Kai Hsiao said:

Which application need to have lower power ? Which situation need to faster filter settling ?

In general, if the application requires running off of battery, if it has a high channel count, or if it is in a sealed enclosure that doesn't provide any ventilation, then power consumption may be a big concern.

The faster settling digital filter modes allow for more data throughput when multiplexing through channels. Also, faster settling times allow for better time-domain response and detection of step inputs. However, the trade-off with all digital filters is that a fast time domain response usually means a worse frequency domain response, so while a filter may settle quickly it will not provide as much noise rejection.

The decision to use a specific filter type may depend more on the environment than the application itself. For example, if a system is required to operate in multiple countries or regions that have different power line cycle frequencies, then using a filter mode that provides both 50 and 60 Hz noise rejection may be important.

Best regards,
Chris