I am working on a design with photodiode (S16838-01MS) to measure ambient lights as well as photo strobes.
I built the design using ADL5303 and I also tried it first using devboard. At testing I found most promising solution placing photodiode via VPDB, however after final design I noticed different behaviour:
Starting with normal ambient light conditions, VPDB is 600 mV (towards GND) (stage 1).
After light comes over certain level, output goes to zero (stage 2, VPDB still at 600 mV then) and then after some more light (let's say stage 3), output is active again (VPDB jumps to 1,1V and then increases with more light).
The most strange thing is this: we did those tests on devboard and there starting VPDB voltage was approx. 1,8 V and output behavour was "normal". After we produced first 1o prototypes I noticed this and started investigating (found no difference in schematics from devboard) and then I switched ICs. From that moment on, both boards acts as described in the beginning (also when I replaced ICs once more, so devboard has original chip on it again). To prove this we ordered additional devboard, which also acts as described in the beginning.
For now (client needs prototypes for preliminary testing) I was able to make a workaround by supplying voltage from 3V3 rail instead of VPDB and this solution works (but offcourse it's not adaptive).
Can you please review this and let me know what we might do wrong?
Best regards,
Gregor MACEK
