ADS1293EVM: what is the time delay from the input of ADS1293 to the output of the evaluation board.

Hi,

TI doesn't provide the time delay info as it could depends various settings(e.g. clock, SPS, SCLK, etc) and the GUI doesn't probability as there are OS and several applications and software in between.

Note- even on chip time delay it also still depends on various factors e.g. CLK, SCLK, SPS and digital Filter selection/settings.

Also, it depends on how user define the delay? User can refer to datasheet page 37 Figure 29

e.g.

delay between the signal starts and the DRDYB pulls low, which depends on the settings mentioned above

or delay between the signal starts and the beginning of SDO, which depends on how soon the host pull the CSB to low and also the settings mentioned above

or delay between the signal starts and the end of SDO, which depends on how soon the host pull the CSB to low and then High and also the settings mentioned above

And from the figure, it indicates that there are at least 8 ~ 9 SCLK(depends on the host) cycles needed for data to come out and roughly 16~17 clock cycles for the SDO to serialize out.

By referring to datasheet section 8.5.7 and Figure 30, it indicates that in the continuous mode, DRDYB is asserted every 1/ODR, i.e. it depends on the Output Data Rate user sets/selects.

If one really wants to measure the time delay between the input(e.g. using Lead RA-LA as shown in ADS1293 EVM user guide schematic and Data sheet page 63) and output, one could probably try the following steps -

1. disable the ECG RA-LA simulator(the signal source generator) output.

2. Connect the signal simulator/generator to the desired input pins on EVM. And, yes, you may need differential oscilloscope or differential probe with Gain to probe on the input pins or use the subtraction MATH function of the scope.

3. select the desired channel, gain and output data rate for ADS1293, and you will also need to probe pins - DRDYB, CSB(depends on the host), SDO.

4. Observe the stable patterns of the differential probes, DRDYB, CSB(depends on the host), SDO when no signal is injecting. Then you probably want to set/adjust the trigger probably for the oscilloscope on the differential probes channel. And use single function of oscilloscope to let the inject single do the trigger.

5. enable the output of the simulator or signal generator, it would be nice to use impulse or step or square wave so it's easier to see/observe how SDO changes and then become roughly stable.

6. You can probably measure the time difference between the signal channel and DRDYB or SDO on the scope using cursor.

Thanks

Hi ChienChun, thank you for the reply, if I need to program the device with a bandpass filter between 62Hz and 0.75Hz, is that possible? how would I do that? Also if I need to program a gain of 400 is that possible to do?

I think the relevant settings are:

delta_sigma modulator

digital filter

how should I configure these settings to get what I am looking for?

Thank you,

Hi,

Would you please clarify "program the device with a bandpass filter between 62Hz and 0.75Hz, is that possible?"?

ADS1293 is not a microcontroller nor have computing power, you can only write/read data to/from ADS1293.

You may design an analog filter or program filter in your host/master(MCU or FPGA. etc) or do it in computer side.

Also not sure what you mean by Gain = 400? ADS1293 has fixed Gain = 3.5 and it's not programmable gain.

May I know what might be your application? Do you want to consider our other ADS1x9x devices or AFE4xxx devices?

Feel free to let me know if you would like to have private email discussion.

Thanks.

It is for biomedical application. Yes a private email discussion might be better.

Hi Lejun,

I will reach out to you via email.

I am assigning this ticket as waiting.

Thanks.