Hi Chris, Thank you for the response. We changed the AVDD of ADS1256 to 5V from 3.3VDC. All channel sampling is done with PGA set to 1. As the AVDD is set to 5V, the input voltage AINx should not be a problem. We have replaced the ADS1256 with new IC before testing with 5V AVDD. We could share the complete schematics if required for your reference. Following are testing done and observations: Changed 3.3V AVDD to 5V AVDD. Still the problem is observed on the 3.3V rail, the voltage drop to nearly 2.9V, resetting the micro. Changed battery from Duracell to Lithium Ion 4.2V as the input to TPS63020 , Still the problem is observed on the 3.3V rail, the voltage drop to nearly 2.9V. Comparatively on the fully charged battery it is less. Changed battery nominal voltage from 2 batteries in series to 3 batteries in series Still the problem is observed on the 3.3V rail, the voltage drop to nearly 2.9V, resetting the micro. The analog section (except the ADC) of the board is powered individually. e.g. temperature measurement circuit is powered and readings are taken and powered down, pH measurement is powered and reading are taken and powered down. The problem is not noted during the power on of the section or power down of the section of the circuit. It is specifically noted when the channel change is done.Please find the attached screen shot of the oscilloscope capture. The Small drop noted at 3ms scale is the power ON of the particular section, the waveform signifies that the load more capacitive. The Second drop noted at 3.5ms is when the channel settings are done, the waveform signifies a Inductive load which we do not have on the board. We are currently writing in to 4 registers (Buffer Register, Channel Register, PGA Register and Data Rate Register). We understand there is a drop in the battery voltage hence the drop in output from the waveform. What we do not get is why the sudden inrush current, since the ADC is already powered up. Please note the drop is the 3.3VDC is not captured when the board is powered from Launchpad. Only difference is the TPS63020 is bypassed. With Regards, Muruga
↧
