we use the TMP464 in the arrangement as shown in the image, with devices that have diode connected PNPs or NPNs with the DXN tied internally to GND.
We use a 0R resistor adjacent to the devices to sample the GND potential and connect all these nets via 50R to D- as star point.
The anodes get connected via 50R to the individual channels D1..D4 and have each a 1uF filter cap to D- in place.
50R and 1uF are placed close to the TMP464.
When we try to read the temperatures we receive -256°C (0x8000) for D1..D4 and the open circuit flags are _not_ set. The voltages at the emitters of the temperature sensing transistors are around 0.45V and 0.5V, which seems reasonable.
We tried several beta factors but to no avail.
It would be understandable if the temperature would be inaccurate or noisy due to differences in GND potential, but no reading at all is something we cannot explain.
https://e2e.ti.com/support/sensors/f/1023/p/675199/2485498 suggest that tying DXN to GND should work with TMP464.
Can you please tell us whether this circuit should work with the TMP464? If so, what could be potential issues and ways to troubleshoot?
Thanks for your assistance.