Problem with 74hc164 overheating when given 5V from 7805

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74hc164 heat

Hi guys

I'm using 74hc164 to drive some LEDs . and PIC24FJ96GA010 to give clock pulse

My problem is
its smoothly working when I give power to 74hc164 through my pic development LV24-33(3.3V)

but if try to give 5V from 7805 and clock pulse from LV24-33(3.3V) it is getting heat




Can anybody have idea about this?

Help me please

Thanks
 

Re: 74hc164 heat

Please change the 150ohm resistor to 330ohm or more... 150 ohm at 5 volts gives about 30mA...LEDs are drawing current larger than their operating continous current.
 

    M

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74hc164 heat

Use high ampere output 5V regulator i.e. 3A and always use heat sink with linear regulators

Added after 9 minutes:

And use resistor value accordingly
 

    M

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Re: 74hc164 heat

150 ohm at 5 volts gives about 30mA
Click to expand...
Although 20 mA or less can be actually expected, considering the LED voltage drop and driver saturation voltage, you should also pay attention to this specification:
absolute maximum ratings
Continuous current through VCC or GND ±50 mA
Click to expand...
It requires a load resistor not smaller than e.g. 470 ohm when drivin 8 LEDs.
 

    M

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