Parallel L298N driver circuit help

[Sidco7]

Hello all. New to this board.

I am in the process of fabricating a 'parallel L298N' driver board which uses the L297 controller. I have built and tested a single L297/L298N 3-axis driver board and it works perfectly. Requiring more current capacity, I have tried to copy the single and twin the L298N and have taken care to parallel channel 1 with 4 and channel 2 with 3. For some reason the parallel board doesn't work and I have almost exhausted my trouble shooting with it. I am nearing the edge.
I was hoping someone has tried this already and might share some insight and experiences with doing it.
Any help would be appreciated.
Sid

[pminmo]

You maybe having physical layout issues. You are paralleling in the same IC correct?

[NC Cams]

It depends how much current you're trying to deal with.

A single stage of L298 is supposedly good for 2.5 amps. Yet if you parallel them, you can only tolerate 3.5 amps, NOT 5!!!!!.

Sorry, but if you need more than 3.5 amps (and that is probably a push), you'll need to use discrete components to build an external driver - at least that's whey my application note for the L297/298 indicates.

[Sidco7]

I have been over the layout until my eyes started bleeding last night. I can't find anything out of the ordinary. The data sheets don't really say much about paralleling the chips other than to take care channeling 1 to 4 and 2 to 3.
What happens with the other pins? Do I double the capacitor and resistor values? Just too many unanswered questions. I was hoping someone might have a working circuit diagram or trouble shoot mine for me.

3.5A is sufficient for the application.
Thanks,
Sid

[NC Cams]

Looks like the following pins on the L298 need to be duplex connnected so as to to properly affect a parallel connnection:

2 + 13 to same motor terminal
3 + 14 to same motor terminal
5 + 10 to proper pin on 297
7 + 12 to proper pin on 297
6 + 11 to proper pin on 297

If you didn't connect the pins as shown, the unconnected pins simply won't react to any input signals and the second bridge won't conduct. You did connnect them, didn't you???

Pins 1 and 15 should probably NOT be tied together thru a common sense resistor. Rather, I'd use a unique sense resistor to each channel.

HOWEVER, they should be matched as identically as possible so as to keep the current flow as equal as possible thru the two bridges. Use 1% tolerance or BETTER sense resistors and then match them even closer if you can.

Since the L297 is the 'controller' chip for the 'pass element' (ergo L298). Thus, you do NOT double any capacitor or resistor values used for timing on the L297.

[Sidco7]

In my application data diagram, pins 7 and 10 are tied (not 7+12) Also pins 5 and 12 are tied (not 5+10) Pins 2 and 14 (not 2+13) and finally Pins 3 and 13 (not 3+14) Recheck yours and if mine is wrong, I'll be just a little upset.

Even if pins 1 and 15 are tied with a common sense resistor, there should be at least some power to the motors, or not?

Thanks for the interest.

[pminmo]

"In my application data diagram, pins 7 and 10 are tied (not 7+12) Also pins 5 and 12 are tied (not 5+10) Pins 2 and 14 (not 2+13) and finally Pins 3 and 13 (not 3+14) Recheck yours and if mine is wrong, I'll be just a little upset.

Even if pins 1 and 15 are tied with a common sense resistor, there should be at least some power to the motors, or not?"


Assuming you have the enables tied also you would be correct. You use the same IC with the pins you have identified wired, plus the enables tied also. Without the enables in the correct state, you will not have source or sink motor drive associate with the enable.

[NC Cams]

I stand by my original post.

However, if your connections turn on the bridges with comparabe logic and polarity, they too should work - I didn't check your pinouts.

You might want to pull the chip and turn on each section of the bridge independantly to see if you can light a LED or such. You may simply have toasted/latched a chip. After all, the L298 is a TTL level IC and it woudldn't be that hard to zap one.

[pminmo]

Originally Posted by NC Cams I stand by my original post. However, if your connections turn on the bridges with comparabe logic and polarity, they too should work - I didn't check your pinouts.

Your pinouts are wrong for the multiwatt pkg, 5 goes to 12, 7 goes to 10.

Plus you have to enable them both at the same time, so 6 goes to 11.

[Sidco7]

Here is my simplified circuit. I have built this layout for a single L298 and it works fine. But something is just not right now.
Thanks for the input.
Sid

[NC Cams]

My pinouts were based upon the SGS (albeit dated) DIP application note that I have. If the connections are wrong, then SGS's pinouts are different or the labeling is funky.

There is a different number altogether for the "multiwatt" package which is L293 if memory serves correct. The pinouts are NOT the same for the L293 versus the L298

My pin out connections assumed that the upper left and lower right NPN's were simultaneously turned on and the upper right and lower left NPN's were turned on in the DIP package. The method used by the member was merely a "mirror image" turn on logic - mine was "twins image" assumption.

Either way, the system should work "mirror" or "twins" connected as long as you don't find a way to shoot thru when you turn stuff on.

[ejaz ahmed]

Hello,
I have 3 bipolar stepper motor VEXTA 2 phase 4 wire 1.8 deg 7.5 v 1.07A which paralal port control circuit work with it ? please help me.send me circuit diagram with pcb.
thank you.
ejaz