# Difference between input current and supply current?

I am reading and trying to understand datasheet of ICs.

I am reading this datasheet now : http://www.ti.com/lit/ds/symlink/sn74hc00.pdf

In the table 6.5, there are two parameters namely Ii and Icc. Input current and supply current.

I would like to understand the difference between the two terms?

Can someone please explain with some example for understanding.

Thanks.

## 2 Answers

$$\I_I\$$ is the input current into an input.

Even though it isn't mentioned in the datasheet, I derive this from the fact that $$\V_I\$$ in table 6.3 is the input voltage, then it is "logical" that $$\I_I\$$ is the input current. This current is supposed to have a very small value which makes sense as this is a CMOS inverter and CMOS logic is supposed to have extremely small input currents.

$$\I_{cc}\$$ is the current flowing into the supply pin $$\V_{cc}\$$

Note that any current that is delivered (to a load) by the inverters also flows into the IC via the $$\V_{cc}\$$ pin. We want to exclude these currents so that's why it says: $$\I_o = 0\$$

The only current that flows in this test are leakage currents which are supposed to be small that's why there is only a maximum value listed.

• Thanks. But suppose I have connected some 10mA load at the output of the Ic. My supply current will be this Supply current+load current, right? 40uA+10mA will be my input supply current,right? – Electronic_Maniac Jan 15 at 13:46
• That's correct, but you can neglect the 40 uA as 40 uA + 10 mA = 10.040mA, that 40 uA is less than 0.4 % of the 10 mA. Also the 40 uA is a maximum. In practice it is often much lower than even 1 uA. – Bimpelrekkie Jan 15 at 13:54

Ii is the input current into a gate. Up to 1uA (1000nA) max.

Icc is the chip supply current. It is listed as very little with no loads attached.

The glossary in 12.7 does not seem to address either one. Perhaps the terms are listed in some of the other reference documents.

• Thanks but what is the difference between input current and that supply current? – Electronic_Maniac Jan 15 at 13:43
• Ii is current into one of the A,B pins. Icc is current into the Vcc pin. – CrossRoads Jan 15 at 13:52