Recent PCB update of a 10 year old product with no changes to DAC layout (change to different micro). Output of DAC7731E remains hung at 11.2VDC regardless of what we do. Tried stuffing blank board with ONLY 7731 + pullups on SPI and power supplies, same results. Pulling RST line hard down on blank board as previously described still leaves output (pins 8,9, & 11) stuck at 11.2 VDC. Tried various positions of trimpots on pins 4, 5&6 for span and offset, no change. Identical circuit to Figure 4 in DAC7731 data sheet, with microcontroller interface through optoisolators. Pins 14, 20, 22, 23 tied to 13, 7 (isolated ground). Pins 8, 9 11 tied together for output. Pins 2 & 3 tied together. Supplies =±12 & +5.
Output used to supply 0 - +10V to constant current circuit.
