I'm using a LM2917MX frequency to voltage converter. The input transducer will be either :
- Variable reluctance with a waveform that is ~ +/- 10Vp-p
- Hall effect device with a 0-10V, positive only square wave
I realize the -8 version of the part is better suited for a variable reluctance transducer, however this excludes using the hall effect transducer
So, I need to either clamp the negative transitions of the VR waveform, or limit the current of the negative transitions.
The differential input options (LM2907, LM2917) give the user the option of setting his own input switching level
and still have the hysteresis around that level for excellent noise rejection in any application. Of course in order
to allow the inputs to attain common-mode voltages above ground, input protection is removed and neither input
should be taken outside the limits of the supply voltage being used. It is very important that an input not go below
ground without some resistance in its lead to limit the current that will then flow in the epi-substrate diode.
Some resistance is about as vague as it gets, and I don't see anything in the specifications for protection diode current limit.
Is 10k Ohm enough?
