1
\$\begingroup\$

I was checking this datasheet about a multiplexer. It says:

This device handles rail-to-rail analog signals and consumes less than 4μW of quiescent power.

Checking the tables below it says that Off-Leakage Current is about a couple of nA.

Because of I will use it with 3.3V and an Arduino to control the digitals A0 AI EN, how I know how much the chip consumes and what does quiescent power mean?

\$\endgroup\$

2 Answers 2

4
\$\begingroup\$

Definition of Quiescent current from Maxim:

For an electronic circuit, a quiet state in which the circuit is driving no load and its inputs are not cycling. Most commonly used for the specification "quiescent current," the current consumed by a circuit when it in a quiescent state.

Definition of Quiescent current from TI

Unless otherwise noted in the datasheet for a part, \$I_Q\$ is defined as the current drawn by the IC in a no-load and non switching but enabled condition. “No load” means that no current leaves the IC to the output.

from Xilinx:

Quiescent power (also called static power) is the power drawn by the device when it is powered up, configured with user logic and there is no switching activity

from NXP for an LDO:

Quiescent or ground current, is the difference between input and output current. It describes the current which the LDO consumes by itself. A low quiescent current \$I_Q\$ improves the current efficiency of an LDO


how I know how much the chip consumes

In your application, as per data sheet, the quiescent power is about \$3.6 uW\$ which can be derived from operating voltage and maximum supply current required for operation. enter image description here

Below table also gives information about typical current draw in graphs which can be considered as reliable average data for calculations:

enter image description here

\$\endgroup\$
1
  • \$\begingroup\$ perfect explanation. Thanks \$\endgroup\$
    – NicoCaldo
    Commented Aug 30, 2019 at 12:21
1
\$\begingroup\$

If you disable the circuit using EN then the chip is switched into a low power off state. It will not do anything even if you apply signals to it. The current consumption can be very low, here a couple of nA.

Quiescent means that the circuit is "awake" and fully functional but simply not doing anything. If you apply a signal to the chip it starts "doing things" which can increase the current consumption. Quiescent does NOT take that into account.

The quiescent power (or current) consumption is for the condition that the signals do not cause extra power to be used. If the chip needs to deliver a current, that current is not considered to be part of the quiescent current.

\$\endgroup\$
3
  • \$\begingroup\$ So basically the consumption depends only if the outputs are connected to something that requests current. If I connect them to a the analog input of an Arduino (for instance) consumption should be very low as well, am I right? \$\endgroup\$
    – NicoCaldo
    Commented Aug 30, 2019 at 9:55
  • \$\begingroup\$ No, not "only if". Chips consume additional power simply by processing signal inputs even if the output isn't driving anything. \$\endgroup\$
    – Finbarr
    Commented Aug 30, 2019 at 10:24
  • 1
    \$\begingroup\$ @NicoCaldo think of the quiescent current as like the fuel consumption of an idling car, its not doing anything, but because its switched on, its using some small rate of fuel (equivalent to current in this example), when you start having it react to inputs and drive loads on its output, its like driving the vehicle, there is a component that is constant per time, and there is a component that changes based on how your using it. \$\endgroup\$
    – Reroute
    Commented Aug 30, 2019 at 11:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.