Hi,
I have an ADS131M03 in my design - and it has been a great ADC so far. I would like to implement a self-check in my firmware and the part has internal test signals as per section 8.3.9 in the datasheet.
When I set CHx_CFG to 0x00 (x = 0, 1, 2), I get the expected voltages for my circuits, e.g.
Measured: CH0 = 0.081795 V, CH1 = 0.495833 V, CH2 = 0.000132 V
and these voltages are spot on. I don't use the PGA, i.e. gain = 1. Now when I want to activate the test mode I set CHx_CFG to 0x02 (positive test signal, as per section 8.6.20). I just get zero signals:
Measured: CH0 = 0.000004 V, CH1 = 0.000002 V, CH2 = -0.000005 V
Same for CHx_CFG = 0x03 (negative test signal).
Measured: CH0 = 0.000001 V, CH1 = -0.000005 V, CH2 = 0.000013 V
CHx_CFG = 0x01 shorts the AIN- and AIN+ as expected.
Measured: 0.000005 V, CH1 = 0.000013 V, CH2 = -0.000006 V
What am I missing, please?
Thanks
Martin
