L298 Hot !!!

[bryan]

All:

Driving a Powermax II stepper motor with a L298. Approx 22vdc at 2.0 amps. The L298 gets very hot. Is this normal ?. Currently have it on a 3x2" heatsink and it is running at around 65 Celcius.

Cheers

 

[Nigel Goodwin]

Yes it sounds normal, drivers do get hot - is the heatsink a proper finned one?, or just a metal plate?.

 

[bryan]

Yes a finned aluminum type using heat sink compound. Guess it's normal with the current draw I am drawing...

 

[Nigel Goodwin]

Yes a finned aluminum type using heat sink compound. Guess it's normal with the current draw I am drawing...

Do the sums, work out how many watts it's dissipating.

 

[crutschow]

According to the data sheet it can drop 4.9V maximum at 2A. That's nearly 10W, so yes the device will get hot with a 3x2" heatsink. The device thermal resistance is 3C/W junction to case, so at 10W and a 65C heatsink temperature, the junction is at 95C, which is below it's absolute maximum junction temperature rating of 130C.

 

[bryan]

Thanks Carl. Looks like a bigger heatsink is preferable, or perhaps a small fan.

 

[Ubergeek63]

Thanks Carl. Looks like a bigger heatsink is preferable, or perhaps a small fan.

get a different chip ... the L297 is an antique piece of garbage! ditch it and it's darlington output stage for a FET part that can do synchronous rectifying for you.

 

[bryan]

You mean the L298??. Any suggestions for something better.

 

[Ubergeek63]

You mean the L298??. Any suggestions for something better.

Sorry yes, the L298. The L297 is the controller typically used with it.

Vsat on the thing is 3-5V. At 2A that is 6-10W if you do not add external diodes.

The Allegro **broken link removed** is a FET output 2.5A driver with 0.9Ω total for 1.8W total losses with synchronous rectifier outputs and micro stepping built in.

Dan