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[SOLVED] need protection circuit for controller low voltage requirement

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ud23

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hi all I am having 3.3v sterallis(lm3s8962) controller and i am using lm7805 for the circuit power supply many times 7805 blown out due revers voltage or high current and it damage my controller. is there any circuit or protection device which block voltage more then 3.3v after lm7805 stage so if lm7805 damage then direct supply voltage 24V cant go to controller??
 

Re: need prtection circuit for controller low voltage requierment

The regulator can't be damaged for high output current because it has internal protection, you can use a diode to protect it from reverse voltage

Check page 11 **broken link removed**
 
Re: need prtection circuit for controller low voltage requierment

Um... am I to understand that you are powering the lm3s8962 directly from the LM7805? The LM7805 is a 5V regulator and you are using a 3V3 processor.... You need a 3V3 regulator to power up that processor.
 

Re: need prtection circuit for controller low voltage requierment

@Alexan_e
I was searching for the reverse diode protection method for 7805 circuit.
The above link is useful. Somehow, I didnt find it in 7805 datasheet which I have.

By the way, can't we use 1N007 diode?
I have used 100uF/25V cap at output in 7805 circuit and 1000uF/25V cap at input.
How to decide which diode to be used? I mean what would be design steps for it?
 

Re: need prtection circuit for controller low voltage requierment

I'm afraid I can't answer your question for the design steps you should use.
According to the 78xx datasheet no protection diode is required for values of output capacitance ≤ 10µF.

Alex
 

Re: need prtection circuit for controller low voltage requierment

@RossiRPI: i am using 7805 to input 3.3v ldo dear so i give 3.3v from ldo not from7805
 

Re: need prtection circuit for controller low voltage requierment

hi,

You can place IN4007 diode in output to input to discharge the voltage when the Main power get off. If you did place any diode, it will discharge through the regulator. It may be the cause for the damage.

5V regulator --> 3.3 V --> MCU VCC
 
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