Over temperature Protection circuit.

[Y.C Park]

Hi Experts!!!

Please give me a advice or other solution for below circuits.
It's a over temperature protection circuits.

Thanks!!!

 

[martinisonline]

If you are looking for a over temperature circuit you can try the TC621C chip of Microchip. Its very simple to program the temperature, just some resistors. look the datasheet.

greats.

 

[muldersun]

This circuit is normally in many IC deisgn,but you need to add the hysteresis circuit

 

[Y.C Park]

Thanks for your reply.

I think if the over temperature protectioon is active, the chip is shut down.
Why the hysteresis is needed?

Please give me some advices to me.
Thanks!!!

 

[IanP]

Histeresis is always used to prevent oscillations ..

In your circuit, depnding on values of other components, ≈1MΩ - 10MΩ resistor between compartor output and (+) input can be used to implement small histeresis .. and ensure stability ..

 

[leebluer]

hello,

I also want to get some guide on over-temperature protection circuit. what is the typical structure? what should I pay attention to during design?

Thanks

 

[Y.C Park]

Dear all

I had already designed the comparator with hysteresis on the main signal path.
Only one side hysteresis is a good approach.( insert hysteresis into uninformation action active)
Hysteresis is a good solution to prevent from chattering.

Now I wondering about inserting hyteresis in OTP.
OTP is a indepenant block.
if OTP is active, I will turn off the bandgap reference and chip Reset signal active.

Could anyone tell me which is right?
( Hysteresis or Not hysteresis )

Thank you !!!

 

[ambreesh]

Why do you want the BGR to be turned off?
We would be using the OTP circuit to shutdown the devices responcible in generation of heat.

 

[Y.C Park]

Dear ambreesh

The purpose of using OTP is protection of Power MOSFET in my design.
I have not yet decided exactly that how to protect the internal circuit and turn on sequence and turn off sequence.

Could you recommand the method?

 

[martinisonline]

You can use this small design with hysteresis, and you can change the R1, R2 and R3 values, but it's not recomended the use of resistors with a value very high like MΩ.

If you don't use hysteresis, at the point of transation, the system stays instable.

greats

 

[lastdance]

Generally, if you shut down your circuits at 150C, u should only reenable it when temp dropped to 120C.

 

[ambreesh]

Hi,
So we must design a thermal loop, if we want the circuit to become active again once the temp falls down.
I was designing a Li-Ion battery charger and did implement the same concept their.
But did not shutdown the system, rather the current through the power mos was reduced or controlled by the thermal loop.

Dear Y C Park,
Could u eleborate more please.
As lastdance has suggested u would also like your circuit to become active again once the temperature has gone below the threshold value.
We would need some way of sensing the same on chip. Easiest would be voltage across a diode with a fixed current source pumping current into it. This could be compared with reference voltage. (buffer BGR, have a voltage drop across string of resistor). The comparator must have internal hystersis.

hope it helps