• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 130 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM393B: Unused channel

Atsushi Hirai
Expert 4170 points
Part Number: LM393B

Tool/software:

Hi team,

I read SNOAA35 application note but, I cannot understand why 10k resistor is required between VCC and unused input.

I understand a resistor between GND and unused input is requied to limit the current due to ground potential difference.

Could you explain why a resistor between VCC and unused input is recommended?

Best Regards,

  • 0
    Guru 280680 points

    The application note says:

    No inputs can be connected directly to low impedance nodes such as ground, VCC or VEE.

    The reason is that during power up/down, different power supplies might ramp up/down at different times, so it might be possible that the input sees an invalid voltage. In that case, the current into the input must be limited.

    If the input connections and the LM393B itself use the same power supply, and if there are no large current spikes in the traces between the inputs and the LM393B's power supply pins, then such an invalid voltage cannot happen, and you do not need resistors.

  • +1
    TI__Expert 5290 points

    Hi Hirai-san,

    It's recommended to connect a current limiting resistor to any low impedance source regardless of any possible fault condition in order to protect the device from large input currents.