l298p heating in the cicuit

[aslamshaikh42]

in the given circuit l298p get heating
can any body tell me why is this heppening
at the output of ic i have connected 12 v dc high torque geared motors
at one output there are two motors

 

[MikeMl]

What supply voltage? How much current do the motors draw? How big a heat sink are you using?

 

[audioguru]

Aslam,
I guess you didn't look at the datasheet for the L298 that clearly shows its max saturation voltage loss that you multiply with the load current to determine how much heating. The datasheet also shows the thermal resistance for you to buy a suitable heatsink.

 

[Boncuk]

The data sheet also shows fast recovery diodes to be used with inductive loads!

Boncuk

 

[audioguru]

The data sheet also shows fast recovery diodes to be used with inductive loads!

Since the very important diodes were not used then the L298 is probably destroyed.

 

[crutschow]

It's truly amazing how many newbies build circuits without ever understanding (or perhaps even looking at) the data sheets for the parts they are using, and then wondering why they don't work.

 

[Boncuk]

It's truly amazing how many newbies build circuits without ever understanding (or perhaps even looking at) the data sheets for the parts they are using, and then wondering why they don't work.

I guess many circuits even work when omitting very important parts. The problem is just the drastically reduced life time of the chips.

Boncuk

 

[aslamshaikh42]

What supply voltage? How much current do the motors draw? How big a heat sink are you using?

SUPPLY=15V
Io = 180mA 4 MOTORS
CONNECTION IS AS SHOWN IN ATTACHMENT
ONLY POWER PAD OF IC IS USED AS HEAT SINK

 

[Boncuk]

Your attachment does not contain the necessary recovery diodes!

Boncuk

 

[audioguru]

Do your motors draw only 180mA each when they are working? Then they are not high torque, they are just little motors.

The datasheet for the L298 shows a max saturation voltage drop when the load current is 1A. Your load current is 360mA for each of the 4 outputs so the saturation voltage drop for each output might be 1.2V. Then each output causes heating of 0.36A x 1.2V= 0.43W and the L298 heats with a total of 0.43W x 4= 1.72W.

The datasheet shows that without a heatsink its chip heats 35 degrees C above the ambient temperature for each Watt. So the temperature rise is 1.72W x 35 degrees= 60.2 degrees. If the ambient temperature is 30 degrees C then the chip is 90.2 degrees C which is pretty darn hot.

Why don't you bolt a heatsink to the metal tab on the L298N IC? Or do you have the L298P in the tiny surface-mount package that will get much too hot unless it is fastened somehow to a heatsink?

 

[aslamshaikh42]

What supply voltage? How much current do the motors draw? How big a heat sink are you using?

supply voltage is 12v
motor all 4 motors are consuming 180mAs
no heat sink is used only power pad of ic is used as heat sink
all voltages are as per datasheet

 

[audioguru]

1) I asked if each motor draws 180mA for a total of 360mA per output.
2) I asked if you have a big normal size L298N with a metal tab, or if you have a tiny surface-mount L298P that is difficult to cool.

But you did not answer.

 

[aslamshaikh42]

1) I asked if each motor draws 180mA for a total of 360mA per output.
2) I asked if you have a big normal size L298N with a metal tab, or if you have a tiny surface-mount L298P that is difficult to cool.

But you did not answer.

i m using l298p surface mount
each motor draws approx 35 mA

 

[aslamshaikh42]

Do your motors draw only 180mA each when they are working? Then they are not high torque, they are just little motors.

The datasheet for the L298 shows a max saturation voltage drop when the load current is 1A. Your load current is 360mA for each of the 4 outputs so the saturation voltage drop for each output might be 1.2V. Then each output causes heating of 0.36A x 1.2V= 0.43W and the L298 heats with a total of 0.43W x 4= 1.72W.

The datasheet shows that without a heatsink its chip heats 35 degrees C above the ambient temperature for each Watt. So the temperature rise is 1.72W x 35 degrees= 60.2 degrees. If the ambient temperature is 30 degrees C then the chip is 90.2 degrees C which is pretty darn hot.

Why don't you bolt a heatsink to the metal tab on the L298N IC? Or do you have the L298P in the tiny surface-mount package that will get much too hot unless it is fastened somehow to a heatsink?

thank u very much for replying me
sir in the datasheet the parameter
Rth j-amb Thermal Resistance Junction-ambient Max. 13 (*) °C/W
is given from it i hv calculated the temprtr as follows
1.4(vtg drop in ic)*55mA(current per motor)= 0.077W

For 4 motors it is 4* 0.077=0.308

temprature in `C is 13*0.308= 4.004 `C

So this much heat is generated in what time
& this the temprature of IC above ambient temp

pls reply thanks

 

[audioguru]

The datasheet for the L298 shows that its thermal resistance is 13 degrees C per Watt only for the tiny surface-mount package and only when it is mounted on an aluminum substrate for cooling it.

The voltage drop for the IC is about 1.2V for each output at your low current. There are 4 outputs. So the max total power dissipation is 0.528W.
The tiny IC will probably overheat if it is not mounted on an aluminum substrate for cooling. Without a heatsink then it will overheat very quickly because it is small.

 

[aslamshaikh42]

The datasheet for the L298 shows that its thermal resistance is 13 degrees C per Watt only for the tiny surface-mount package and only when it is mounted on an aluminum substrate for cooling it.

The voltage drop for the IC is about 1.2V for each output at your low current. There are 4 outputs. So the max total power dissipation is 0.528W.
The tiny IC will probably overheat if it is not mounted on an aluminum substrate for cooling. Without a heatsink then it will overheat very quickly because it is small.

thank u sir

 

[aslamshaikh42]

The datasheet for the L298 shows that its thermal resistance is 13 degrees C per Watt only for the tiny surface-mount package and only when it is mounted on an aluminum substrate for cooling it.

The voltage drop for the IC is about 1.2V for each output at your low current. There are 4 outputs. So the max total power dissipation is 0.528W.
The tiny IC will probably overheat if it is not mounted on an aluminum substrate for cooling. Without a heatsink then it will overheat very quickly because it is small.

sir i hv mounted it on the luminium substrate by soldering it for proper heat transfer but then also it is getting hot quikly
can you pls guide me for this problem
on Vs pin i m giving 12v & at Vss it is 5v

 

[audioguru]

You cannot properly solder to the tiny IC and I do not know how to "mount it" properly because I have never seen one. Use the normal big IC instead with a real heatsink.

 

[RMMM]

Use a CPU or memory heat sink and a dab of thermal paste to put a heat-sink on the IC.

Did you add the diodes into the circuit?

 

[Ubergeek63]

Use a CPU or memory heat sink and a dab of thermal paste to put a heat-sink on the IC.

Did you add the diodes into the circuit?

i really wish that miserable, obsolete piece of crap would be discontinued. for the cost of that garbage you can get a step and repeat chip with mircrostepping and synchronous rectification.