Cannot Enable 3 TMC389 at same time

[japhy]

Hi, Mr. Dwersteg,
Now I got my 2nd version of prototype board. I faced a new problem. When I enable 3 TMC389 at same time, only 1 or 2 motors can be locked. rest of them was free wheel. But if I just connect 1 Motor to the any of 3 TMC389, it's perfect. I've tried any possible to avoid this issue, but it's just there.

My hw config is:
Motor: 5.8A peak, 1ohm
Rsensor: 0.1 ohm
MOSFET: IRZL44N + F9Z24N
Vm = 24V

TMC389 initalization datagram is use the code presented at 2nd last page of datasheet.

Also, Just after 5 to 10 minutes, the MOSFETs and TMC389s got very high temperature and the finger cannot touch with long time. I tried to read the status code of TMC389, the one with good status would return 0x10, 0x34 while other self-disabled IC would return 0x80 or 0x90.

Please advise any other important parameter I did noticed?

[TRINAMIC_BD]

Hi Japhy,
unfortunately the error flags look a bit weird - may it be they are shifted by one bit? As a clue, you will always see bits 4 and bit 6 and bits 8 and 9 = 0.
I.e. a response 0x00010 cannot be, because bit 4 will always be zero. Please try figuring out the correct response, then we can see what the mean.

I guess, your power supply drops down to zero for a short time, when you enable the second or third motor, so that one or more drivers become reset due to undervoltage. Can you please measure? If this is the case, please try adding a large capacitor, e.g. 10000µF on your power supply.
For MOSFET temperature, you should make sure, they stay below 100°C - some heat up is normal at high current. This might be less, when you use standby current reduction.

[japhy]

Mr. Dwersteg,
Yes, I was wondering that why those reserved bits are become 1. Since they are unused, I never take note on that. I will follow this clue to investigate.

Additional questions here:
1. How to improve TMC389 hot problem? After 10 minutes, I got pro-OverTemp warning.
2. How to reduce Standby Current? I tried to setup SMARTEN register, but only reduce about 20% current with big noise side effect.
(Currently my FW consept is just initialize TMC389 once and then handle to TMC428.)

Best Regards,

[TRINAMIC_BD]

Dear Japhy,

the TMC389 should not become very hot itself - unless you have much additional load on the +5V output. But, it is important to have the exposed pad under the IC soldered and contacted to your board GND plane with a number of wires, in order to dissipate heat. Then it will heat up by 15 to 30°C, depending on the supply voltage.

I have looked up your MOSFETs: The N-Type IRFZ44N has a quite high gate charge, which makes slopes slow, and is non-optimum with 5V gate drive. When I check IR types, IRLZ44ZS or IRLR3105 or IRLR2905Z or similar would be better (all 55V). The P-Type has a quite high resistance, IRFZ9Z34 would have less. If you have the chance to purchase them, SUD23N06 and SUD08P06 are a very good choice.
In case, you do not need 48V supply, there are MOSFETs with better RDSon and less Qg, e.g. 30V types or 40V types. Also, a FDD8424H will improve power dissipation by a factor of 3, I guess. We found it is good for 5 to 6A, also! (do you have the TMC389 Evaluation board? - you could test by swapping sense resistors).

For reducing standby current, you need to make SW interaction. You could use the TMC429 position reached interrupt, to detect stand still of motor. Then you need to write to TMC389 a reduced current setting. When you start the next move, you need to increase the current again before start.
The coolStep function in the SMARTEN register will not help for motor stand still. It will help optimizing power at a medium velocity (not too low, not too high), when your motor runs for a long time at this velocity (e.g. at VMAX during a normal move).

Best regards,
Bernhard

[japhy]

Dear Mr. Dwersteg,
So Appreciated with your clear directions! I've resolve my issue with very short time, after put a new 22000uF to 24V.

The type of MOSFET was also bother me a few days since it's hard to find high reqirement components with TO-220 footprint. Now not any more.

I don't have a TMC389 Eval board with me but instead of TMCM310G since at that time the 389 eval-board was not available yet.

Thanks again.