Connect ADS1298ECG-FE with TMS320C748 LCDK (ADS1298 + C6748)

Hello Brian and Senthil,

thank you for your help. The power spreadsheet is helpful.

What do you think about the headroom from "typical 456 MHz" to "typical 300 MHz" configuration of 660 mW - 427 mW = 233 mW
The DSP should be operating at 300 MHz, probably fixed for the LCDK. But I don't know if the power supply is laid out for the higher power consumption at the higher frequency.

A rough estimation of the power consumption for the ADS1298 board would also be helpful. The "ADS1x98ECG-FE Power-Supply Recommendations" state
• Output voltage: 5.5 VDC to 15 VDC
• Maximum output current: 500 mA

But this obviously includes the power of the MMB0 motherboard (DSP C55x + peripherals).

[Edit: from the ADS1298 datasheet itself "Low Power: 0.75 mW/channel", but I am rather looking for max.]
 
I'm not sure if somebody can provide me the measurement equipment here. Because I read somewhere that you can use jumpers JP4 and JP24 to meaure the current by plugging in an amperemeter instead, but I haven't checked so far.

Could you please also elaborate on the +5V power supply question?

Thank you in advance.

Best regards,
Matthias

Hello Brian,

thank you for your response. In the meantime I also tried to measure the power consumption in different modes of the ADS1298ECG-FE when being connected to the MMB0 board. I used the JP4 and JP24 connectors with two ampmeters. On the +5V rail it drew about 18 mA and on the +3.3V rail about 18 mA while acquiring through the NI software. However these values did not significantly change when toggling between hi-res and low-power mode and 500SPS or 1000SPS. Changing between 8 channels and 1 channel did also not seem to affect anything.

I think I haven't done anything wrong but the MMB0 is no longer responding. Can you please give any guidance for checking the board for defects? I also have an XDS100v2 if reflashing or debugging is necessary. The 7 segment display of the module was showing a "b." without the lower left segment (or "5." without the upper segment). IIRC this is a status display. At the moment it's completely switched off. Could this also be a driver problem? When does the 7 segment display light up?

Edit: the ADS1298-FE itself is a Rev. A3. I think the schematics might have changed. Is it possible to check the different revisions?
 
Thank you for your help.

Cheers,
Matthias

Hello Brian,

thank you for coming back to me. We did not change jumper settings, except JP4 and W7 for inter-changing them with an ampmeter each. We also measured the voltage. W7 on Rev. A3 board is hopefully the equivalent of JP4 on the Rev. C board. Can you please provide the schematics for our older PCB revision?

My colleagues PC did a "driver update" during the board was plugged in and the NI application crashed. Can the flashed firmware be corrupted?

In the meantime I tried to interface the ADS1298FE without the MMB0 motherboard directly via SPI. The ID register reads 0x52 instead of the expected value 0x92. According to forum posts the device may be damaged or the start-up sequence is not correct. In order to check the start-up sequence it may be helpful to check the VCAP1 voltage.

I did not find a testpoint for this, but it can be measured next to C33 or C9 according to the schamtics (Rev. C). As we have Rev. A3 I don't want to experiment with the part IDs as the numbering may have changed. Again the schematics of the old revision can be are helpful here.

Edit: we were successful in connecting the ADS1298-FE with the MMB0 motherboard to the PC again, using the USB connection. The download of the Firmware was succesful and the test square wave could be seen in the scope of the PC application. However, the ID reads 0x52 also in this application. Furthermore "Figure 16. Device Registers Settings" of SBAU171D–May 2010–Revised January 2016 reads a value of 0x52 for the ID register.

Please confirm that also 0x52 can be a working identifier (the MMB0 should do the start up sequence right, and the board or ASIC is not damaged). Please also let me know why the datasheet does not list this ID as a valid one (3 MSBs combination neither listed valid nor listed reserved).

Maybe also a case of "pre-production silicon", see https://e2e.ti.com/support/data_converters/precision_data_converters/f/73/p/140996/518343#518343 ?

Hello Brian,

thank you for your response. it was quite helpful. I managed to write and read registers of the device.

However the samples themselves seem to be noisy in two channels (channel 2 and channel 5), when using the square wave test input signal.

The gain is programmes for factor 6, sampling rate is 500 SPS in low power mode. Do you have a clue why this is?

Cheers,
Matthias