Power estimation of IC's

[Bjtpower]

Hello Guys,

I want to calculate the Approximately Power required for the IC (LM339 or KZ8081RNA)

Which parameters are taken consideration while calculating the same..?

Kindly help for the Same by giving datasheet reference as an example so it would be easier to understand me as well the ppl who use this Forum.


Regards,
Marx

[schmitt trigger]

Quiescent or operating?
With or without load?
At its minimum or maximum voltage?

I will be looking at TI's datasheet revision E when I mention figures.

1) I would start by reading the datasheet's supply current vs. voltage and temperature. Figure 1. Multiply by supply voltage.
2) Then take all the output load currents (which include the pullup resistors, use ohm's law), and multiply it by the output saturation voltage, figure 3.
3) The losses dissipated by the actual switching....that will be a tough one as it is not specified. But as a ballpark value, if you are switching slowly, below 1 KHz, leave the sum of 1 and 2 as is. Add 10% for each additional decade of switching frequency. Again, this is only a ballpark value.

[Bjtpower]

Hi..
Coming to the Controller.
I am using controller STM32F417IGH6.

Now i want to make a proper calculation for the same.
http://www.st.com/en/microcontrollers/stm32f417ig.html

Now the controller will be operated on the +3.3V
i want to understand the current so i will design the Power supply of the same by keeping 20% margin of approximately result.

Regards,
Marx

[KlausST]

Hi

In my eyes it makes no sense to use a power supply just for the microcontroller.
I recommend to deign the power supply for the complete circuit, including all other ICs, resistors, LEDs, interfaces...that are connected to the microcontroller.

And take care of proper input voltage levels.
Usually the supply current is specified with all inputs tied to VCC or GND.
If in your application there are input pins floating or connected to voltage levels far away fro VCC or GND, then the Icc may be increased. Don't be surprised if you see twice or more the ICC given in the datasheet (depending on microcontroller operating state).

Usually this is also explained in the microcontroller datasheet.

Klaus

[dick_freebird]

The datasheets are pretty plain about maximum and
typical Icc. I am not going to post them, datasheets360
has everything you could want.

Add to this the load (pullup) resistor current although
this is not truly -IC- power dissipation and depends
on circuit state and is often a different supply than
the IC's operating supply.

You're talking tens of milliamps including load current
if you do the arithmetic.

[Bjtpower]

Hi

And take care of proper input voltage levels.
Usually the supply current is specified with all inputs tied to VCC or GND.
If in your application there are input pins floating or connected to voltage levels far away fro VCC or GND, then the Icc may be increased. Don't be surprised if you see twice or more the ICC given in the datasheet (depending on microcontroller operating state).

Usually this is also explained in the microcontroller datasheet.

Klaus

Hi Klauss.

if the Input pins will be floating, then how it can consume current.

Another, I want to Make specification for the Micro controller.
Where i am conflicting between the Max power Dissipation..? and Max current ICC..??

Which current need to be taken into consideration..

or Are there any other ways..?

[dick_freebird]

If you are concerned about thermal issues then think
in terms of power.

If you are specifying or designing power delivery then
think in terms of current draw in each supply voltage
branch, and work up your budget subtotals.

Floating inputs mean an undefined internal state
while supply current is specified and tested under
very specific (often, only one) condition which has
everything defined.

For your linear comparator you might see no supply
current difference (if open inputs drift apart and
create an opportunistic "signal" that happens to be
close to test conditions) or you could see greatly
elevated current draw from the comparators
"chattering" when inputs happen to be close together
and back-coupled ground noise sets up a ground
loop oscillation (output->gnd->input->output).

Your options are to enforce known conditions that
are known not-crazy, or to accommodate a worst
case supply current that exceeds datasheet (by
how much, is an exercise that includes some amount
of fog and futility). And to tolerate any output
uncertainty / activity (which might well impose not-
as-spec'd input conditions on downstream stuff).

[KlausST]

Hi,

if the Input pins will be floating, then how it can consume current.

It's not input current, it's supply current that increases, caused by crowbar currents in the input stage, when both transistors, the highside and the lowside are (slightly) conductive at the same time.

Klaus

[Bjtpower]

Hi,
Here i have attached the OPAMP snapshot to understand the Better.

I am using the OP-AMP 393 in Comparator mode.

Where output is pulled up with the +5V with 2.1K resistor.

Now attached figure is giving me confusion while Current consumption.
Where they have Mentioned the ICC (Supply Current) and If opamp configured in the Comparator.

Which value needs to take for the Power consumption part..?

[schmitt trigger]

Multiply current by supply voltage.

The datasheet snippet is for the LMV393, is that what you are using?

[Bjtpower]

Hi Schmitt,

I have been confused in the Supply Current (ICC) & INPUT Sink current.

For the, Power consumption which parameters are corrent to take in account and why..??

[schmitt trigger]

No need to be confused.
Just follow the steps I outlined in post #2