TIPD197: ADS1298 : Software pace detection

Winston Rodrigues

Part Number: TIPD197
Other Parts Discussed in Thread: ADS7042, ADS1298,

Hi,

By referring to the document here : http://www.ti.com/lit/ug/tidub75/tidub75.pdf Software Pacemaker Detection Reference Design]

In the figure Figure 13 it is mentioned that we are supposed to use SAR ADC for sampling theopamp output signal.

My question is:

Can I feed the op-amp output directly to my microcontroller ADC instead of having another ADC ??

Why do I have to use a SAR ADC for this ?

My Microcontroller ADC specs are as follows:

Sampling rate : 2.4 MSPS

Resolution : 12 bits.

Input impedance : 50 Kohm

Sample and hold capacitor: 4 pF

Thanks,

Winston

over 6 years ago

0 Kevin Lee16 over 6 years ago

Prodigy 190 points

Most likely because for high resolution sampling, the ADS7042 can be digitized and read using one SPI channel from a low end MCU. Instead of requiring an MCU that has 24-bit Analog Input, which is not easy and cheap to find. Unless of course you already using one in your system.

0 Kevin Lee16 over 6 years ago in reply to Kevin Lee16

Prodigy 190 points

Also, the main reason for connecting another ADC shown in your diagram is in the case when you need high and low data rate mix usage in your system. ADS1298 allows user to tap out the PGA[1:8] output and process the signal independently. But if you are not using mix data rate usage, I think you can connect directly to MCU SPI from ADS1298

0 Ryan Andrews over 6 years ago

TI__Guru 59256 points

Hi Winston,

Thank you for your post!

The SAR ADC solution shown in TIPD197 is just an example of how this application could be done. You can a different ADC if you'd like, as long as the sampling rate and resolution meet your performance criteria. The reason a separate ADC is used in addition to the ADS129x is that we cannot run a single channel faster than the others to get the bandwidth needed for pacemaker detection. Many applications require even faster than 32 kSPS, so a higher speed ADC with minimal added power and size was chosen for this application.

Best Regards,

0 Winston Rodrigues over 6 years ago in reply to Kevin Lee16

Prodigy 60 points

Thanks Kevin.

Data converters

Data converters forum

TIPD197: ADS1298 : Software pace detection