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CD4098B-MIL: Minimum Resistance

Scott Taylor21
Prodigy 230 points

Part Number: CD4098B-MIL

What limits the minimum resistance of the CD4098 to 5k? Why not 1k?

  • 0
    TI__Guru* 97676 points
    Hi Scott,
    I would think it's a limitation of the current sinking capability of the discharge circuit. The outputs of this device can only drive a few milliamps -- if you go much below 5k, you will likely run into problems with not being able to fully discharge the timing capacitor.
  • 0 in reply to Emrys Maier
    Prodigy 230 points
    I wondered about that, however the 74HCT123 says the same thing and an existing circuit is using less than 1k and it still works. At least at ambient. I would like to use an RTD to provide temperature variation on the pulse width. The ambient value is 1k. Lower cold and higher hot. It would require six or seven in series to guarantee 5k at all temperatures.
  • 0 in reply to Scott Taylor21
    TI__Guru* 97676 points

    That's the case for many devices from TI (at least in my area: standard logic and translation). I have seen a lot of our customers use parts well beyond their intended operating range and they work well for many years -- but if they asked me, I would have to say that their application goes against the datasheet specs and isn't guaranteed by TI.