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

Cashewmiro

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?

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 319020 points

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

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 V_CC.)

0 Malcolm Lyn over 1 year ago

TI__Mastermind 29470 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

Logic

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