In the datasheet for the MAX15500, it says I need to use several diodes in series:
… to ensure a voltage difference of 2V to 3.5V from AVDD to AVDDO and
from AVSS to AVSSO.
It seems to be that a 2V- 3.5V Zener diode should be able to replace all 5 of these diodes. If so, why are Maxim suggesting such an overly complicated circuit? Am I missing something?
Best Answer
Theoretically, you could use a Zener diode.
However, there are several practical reasons why you would NOT do so.
1) Low-voltage Zener diodes are very leaky. The threshold knee is soft and not well defined. You have to run a fair amount of current through them to reach the rated Zener voltage.
2) Low-voltage Zener diodes are hard to manufacture. The lowest-voltage Zener diode that comes to mind is either 3.0V or 2.8V - (I don't recall which).
For a low-power circuit, a string of series diodes performs much better.