I have a circuit that I need to use XOR gate IC using battery power. The chip in question is 74HC86.
As per data sheet the supply current should be between 20 to 40 micro amp, but , if i just power up the chip using vcc and ground, it is using 3 to 7ma of power. tested different chip but same result , the supply voltage is 3.3v, at 5v, it is taking 23ma. am not sure what mistake am doing. the circuit ultimately would use only one gate, although it has 4.
The Icc of 20-40 uA is static current. You'd notice that it is specified for Io=0A. You'd also notice that the absolute maximum Icc current is specified as 50mA.
You are not doing anything wrong. The 7mA and 23mA that you get are dominated by dynamic current.
If you want to measure the static Icc, then you'd have to ensure that Io=0A.
you might want to see what you get with the input pins all tied low
floating input pins can float high, making an output high, without current
which changes internals and can change supply current
you might want to see what you get with the input pins all tied low
floating input pins can float high, making an output high, without current
which changes internals and can change supply current
If CMOS inputs are left floating, the input voltage is not defined and it can end up at the midpoint voltage where both the N and P MOSFETs can turn on (in normal operation one is fully on and one fully off so only leakage current flows).
That's likely what's causing the observed current.
I once was using a CD4000 series logic gate operating from 12V where I didn't tie down the inputs.
It drew so much current that the IC got hot.
Thank you everybody, so after making the input pins tied to ground, all is normal now, the current draw is at 5ua. the first pcb I made out of general pcb did not show high power usage but the second one did, so thought I made a mistake or bad chips.