I am using AD7190 Evaluation on my project. I am connecting STM32L152 Discovery board (external micro-controller ) to the evaluation board. I am using following set up:
Ref1+ & Ref1-
Ain1+ and Ain2-
ADC mode: Bipolar.
I have set up connector J2 of the evaluation board as :
CS to logic 0
SCLK connected to SPI CLOCK of the external micro controller.
DIN connected to the MOSI of the external micro controller.
DOUT connected to the MISO and external interrupt pin of the external micro controller.
I have used USB to power the evaluation board and placed a jumper on 5V USB pin of J1 connector. I have connected the AGND of the evaluation to the discovery board.
My problem is:
if I place a jumper on the DVDD pin of J2 connector, the ADC value keep jumping i.e. not stable even though the Ain1+ and Ain2- connected to dc input voltage of 10mV. However, if I do not put a jumper on DvDD pin, the AD7190 gives correct value.
Looking at the schematic of the evaluation board, the only way the AD7190 is getting voltage at DVDD pin is by connecting jumper on DvDD pin of J2 connector. In addition, without this jumper connected, I am seeing 2.2V Voltage at DVDD pin of AD7190.
I don't understand how the AD7190 is getting voltage when a jumper is no placed at DvDD pin of J2 connector.