I met a quite curious problem recently. I used AD7324 on my board to sample anolog signals, and the power supply are +-15V, +5V and 3.3V. I am seeing the ADC could be locked up sometimes. Everytime the promblem present, the 4 channels of AD7324 output data 0x8 although the channel number changes nomally.This output data would not recover to normal until power down and up again, even i config the command register to work in normal operation every 500us via SPI. I don't know how does this happen, and by the way, the problem would be occur from power up every time.
Anyone can tell me why? Thanks a lot!
Stuck codes would usually mean an issue with the reference circuit. This article here might help you. I could also have a look at your schematics if you attach a copy here.
Thanks for your reply. I checked the PDF and found the wave form on figure 9 is quite similar with my trouble, i would check my board at the reference. The schematics is not in my computer now, maybe i'would attach it tommorrow if i couldn't fix it tonight. Thanks a lot!
I havn't fix my problem yet, and i attached my schematic below. I used one ADR443 to generate refference VREF for 3 AD7324. As to the PDF file, ceramic capacitors may be the first factor to "stuck" code, but i put 3 capacitors at the output pin of ADR443, and 2 capacitors at the VREF pin of each AD7324, i think the persability of capacitor could be emililated.The second, the PCB has 6 layers, with 2 whole ground, signals have been burid between the 2 ground layers; The third, ADR443 can output 10mA current max, and the static current of AD7324 is only 1uA, so i think supply currrent of VREF should be enough. Could you help me to check the problem again?
Have you monitored your reference during operation? How are the capacitors placed with respect to the AD7324 REFIN pin?