• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 2 answers
  • Subscribers 19 subscribers
  • Views 101 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.

Original question:

SN74HC14: Input voltage above VCC with current limit safe ?

SN74HC14: How to calculate the current going into a channel in 74HC14?

Cashewmiro
Prodigy 20 points
Part Number: SN74HC14
Other Parts Discussed in Thread: SN74AHC14, SN74LV14A

Tool/software:

I have a circuit where a 10V supply is stepped down to 5 using a simple resistor-based divider circuit. How can I calculate the current going into the channel that follows this? What circuit combination (for egs npn and R) can I take as an equivalent circuit for each channel in the 74HC14?

  • 0
    Guru 285550 points

    CMOS devices have high-impedance inputs; the input leakage current is specified as II.

    When the input voltage goes beyond the power rails, a current flows through the ESD clamping diodes; if your circuit relies on this voltage clamping, then the current must be limited externally. (Other logic families like SN74AHC14 or SN74LV14A have inputs without a clamping diode to VCC.)

  • 0
    TI__Mastermind 19900 points

    Hi Cashewmiro,

    Clemens is correct here. Typically for these CMOS inputs beyond the leakage current the only way to know the current value would be to measure it.

    Best,

    Malcolm