I've used the AD9707 DAC in a couple of designs, but one of them is showing an odd failure mode, related to operation at higher temperatures. When I do an initial run at 70degC, it appears to be fine - with static and dynamic inputs. When the circuit is tested with the larger assembly, it slowly ramps up to around 70degC chip temperature again (over a period of several hours), but this time the chip fails: the output goes to full scale and it will not respond to new inputs. If I reset power it starts properly but the output goes to full scale again after a minute or so, even with a static input. It appears to be related to the chip reaching that temperature of about 70degC.
I've used exactly the same circuit in other products without any trouble at all, even operating at temperatures up to 80degC. It's driven by an Altera FPGA in both cases, and drives the same op-amp too. This time I've had two chips fail in quick succession. Has anyone experienced this sort of problem with the AD9707 or related DACs?
I'm wondering if it's a batch reliability issue. The markings on the chips are:
Any tips or things to test are welcome, solutions are particularly welcome!