SN74LVC245A: Input Current Requirements

Sahil Bhat

Part Number: SN74LVC245A

Hi, I am using SN74LVC245APWR IC in my design. My question is what is the current requirements at control pins(OE Pin 19 and EN Pin 1) and the I/O pins as well. As per the datasheet (Section 7.5 Electrical Characteristics), there is delta Icc and Ii current listed, but I am little confused which spec to look at when trying to understand the current requirements at control and I/O pins. Please advise.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 317280 points

Only I_I matters; see Understanding and Interpreting Standard-Logic Data Sheets.

0 Sahil Bhat over 2 years ago in reply to Clemens Ladisch

Prodigy 70 points

Thanks. The datasheet lists Icc and delta Icc current specifications as well. Is that for current on Vcc lines only or does that include control & I/O pins as well? Please advise. Thanks

0 Clemens Ladisch over 2 years ago in reply to Sahil Bhat

Guru 317280 points

I_CC is the current that flows into V_CC and out of GND.

0 Sahil Bhat over 2 years ago in reply to Clemens Ladisch

Prodigy 70 points

Thanks, So as per the datasheet the Ii current should be +/-10uA (max). I have attached my schematic below. Can you please tell if I am using the correct pull up resistor (R216) value on EN pin. or should I change it to some other value? Thanks

0 Clemens Ladisch over 2 years ago in reply to Sahil Bhat

Guru 317280 points

10 kΩ is OK, as is any other value between 0 Ω and 130 kΩ.

0 Sahil Bhat over 2 years ago in reply to Clemens Ladisch

Prodigy 70 points

Thank You for your reply. But please help me understand this: If I use (for example) a 0ohm resistor, won't the current be much more higher than maximum current rated (10uA) for the control pins of that IC. How does the IC behave in that scenario. Please advise.

0 Clemens Ladisch over 2 years ago in reply to Sahil Bhat

Guru 317280 points

The I_I specification describes how much current flows when you apply a voltage directly to the pin (see the test conditions).

Please note that CMOS inputs have an extremely high impedance. 10 µA is a theoretical worst-case value at the highest temperature; typical inputs currents are orders of magnitude smaller.

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SN74LVC245A: Input Current Requirements