I'd be a total NOOB too when looking at this circuit, but I don't like it.
In order to drive the high side MOSFETS you need a voltage greater than the supply. The bootstrap voltage. it LOOKS like it's fixed, so what you have is the drivers not fully on. The 24 V thing is balony.

So, bootstrap has to be greater than the actuator voltage. That voltage is made from a lower voltage, not sourced.

The datasheet suggests that the resistors should be removed from the gates. This is a secondary problem.

it's bedtime for me, so I might not be as coherent.

 

Question, do you own, or have access to, an oscilloscope?

Yes, it's in the picture above

 

Yes, it's in the picture above

Sorry about that... I've been up to my neck with work and I wasn't paying full attention. One last thing before I go to bed. Some MOSFET high side drivers cannot work reliably at full 100% duty cycle. That is, they require some dead time while switching to allow for the external drive capacitor to charge before activating the gate. That's why I strongly suggest you scope both high and low side fets simultaneously. See if some overlapping is happening and find if that's causing the MOSFETs to heat up.

 

Sorry about that... I've been up to my neck with work and I wasn't paying full attention. One last thing before I go to bed. Some MOSFET high side drivers cannot work reliably at full 100% duty cycle. That is, they require some dead time while switching to allow for the external drive capacitor to charge before activating the gate. That's why I strongly suggest you scope both high and low side fets simultaneously. See if some overlapping is happening and find if that's causing the MOSFETs to heat up.

I see what you are saying.
I have different boards coming in today, but I'll hit it with some PWM and see if the characteristics change.
(Is like to learn the proper way to scope the individual mosfets though for educational purposes)
If your theory it's true than that means that perhaps these are good boards but with terrible documentation.
I.e.
1) the test circuit will fry the solder from your mosfets.
2) this board should Never be used without PWM, and never below the threshold level.

Does this schematic look legit?
If not, another issue with documentation. . .

 

The schematic in post #39 looks ok (apart from ambiguity as to the value of the gate resistors). Do your actual board component values tally with the schematic? Are e.g. the correct FETs used on the board?

 

Does this schematic look legit?

I think there is something wrong

I thin it will be messed up when the high side FETS are ON. At 100% PWM look at Vgs of especially the high side FET. That's the supply to the Gate. I think you will find that it's operating in the linear region.
Also look at Vds of each. bet it's also high.

The reason it's high is tat you need Vbootstrap to be higher than Vcc to you can fully turn on the high side FET.
Two 15V things isn;t right. One needs to be 12 and the other 15 to 17V and the 17V generated by the 12 V supply.


Post the links to the datasheets of the IC's/

Can you post the schematic in PDF so I can magnify to be able to see the part number clearly.

The driver does suggest removing the gate resistors. Normally they are suppose to be there.

I believe there is something wrong with Bootstrap and the high side FETS are operating in a linear region. It's not suitable for 24 Vdc.

This is from a casual look at the schematic. No expert.

 

I see what you are saying.
I have different boards coming in today, but I'll hit it with some PWM and see if the characteristics change.
(Is like to learn the proper way to scope the individual mosfets though for educational purposes)
If your theory it's true than that means that perhaps these are good boards but with terrible documentation.
I.e.
1) the test circuit will fry the solder from your mosfets.
2) this board should Never be used without PWM, and never below the threshold level.

Does this schematic look legit?
If not, another issue with documentation. . .

There is some stuff missing from your schematic. I see an inductor on the board. I suspect this "makes" 15 volts for the drivers from either the 5 volts or the motor voltage. Probably the 5 volts.
The drivers in the schematic have what is called under voltage lock out, so I don't think KISS concern is a problem.
They will not work at 100% pwm however. But they should just stop not get hot.
Are you sure your limit switches actually break the circuit to the motor? Or could it be stalled at the limits? Try just scoping both sides of the motor for starters.