heat generation in IC ?

[truebs]

hi friends...

Can you tell me what are the factors that lead to generation of heat in the CMOS IC ....and that too such a level that we need to install a FAN (say in Intel processor) .
And that too when the power consumption is very low ?
Is it just the resisitive parameters ?

thanks

 

[eda_wiz]

hi friends...

Can you tell me what are the factors that lead to generation of heat in the CMOS IC ....and that too such a level that we need to install a FAN (say in Intel processor) .
And that too when the power consumption is very low ?
Is it just the resisitive parameters ?

thanks

Energy is dissipated as heat while charging/discharging of various capacitances inside the circuit. Clock frequency is the main culprit for higher heat dissipation in CPUs. as clock increases swithiching activity increases and more energy is dissipated in unit time.

And that too when the power consumption is very low ?

New Intel/AMD processors consumes 40-100W.. do u think that is too low??
For eg AMD Athlon 64 3500+ consumes around 65W.

 

[peter kabiri]

hi
probably because cmos ICs have a very large packing density....for example some may have upto 1 million logic gates.

 

[truebs]

hi
probably because cmos ICs have a very large packing density....for example some may have upto 1 million logic gates.

so what ? i mean how is density related to the heat generation ?

Added after 29 minutes:

thanks wizkid ...but can you explain me in details....like how the charging discharging would finally lead to generation of heat.

It must be cos of resistance in C ?

thanks

 

[dr_dft]

Packing density may not have direct impact on heat generation, but it does have impact on heat dissipation. The larger the surface area on the package, the better the heat dissipates, and hence the heat sink and fan is needed to keep the temperature inside the chip cool enough to function correctly.

The main source of heat is switching current flowing through resistive interconnects. On one hand the transistors are shrinking, and supply voltages are dropping, causing the power dissipation to drop. But on the other hand, the interconnect widths are also shrinking, and the number of metal layers are increasing, increasing the total resistance.

In the microprocessor world, where clock frequency used to be the measure for performance, Intel was pushing chips to run at higher frequencies. Other than the apparent clock frequency increase, there was another factor that led to higher power dissipation. To achieve higher frequencies, the architecture need to be super-pipelined, meaning that the number of flip-flops or latches on the chip increased significantly, which led to a larger clock tree or mesh. Since the clock is the net with the highest switching activity on the chip, the larger clock network means even more power dissipation.