MP6450 Latch Up

Motor Drivers/Sensors
1

Hello Stephen,

when I interrupt the 24V-Power Supply of the MP6540 for a short time (~ 100ms and BLDC is running) the drive stops and the MP6540 won’t come back in operation.
I have to repower the driver to be able to start the motor again. It looks like some kind of latching.

Heard of this or any ideas?

Best regards

Frank

24V_Spannungseinbruch_5Hz_50_50
24V_Spannungseinbruch_5Hz_50_50800×522 57.8 KB

2

Hello Frank,

Do you mind clarifying what waveform is what here? I can only assume that Channel 1 is the Input and Channel 2 is the PWM Switching, which doesn’t seem to stop after the dip in Channel 1.

Also, I am not sure if Stephen has helped you with the schematic, but would you be able to provide the latest version to further debug this issue?

3

Hello Krishan,

In advance, the 24V-Supply voltage of the MP6540 is switched by a relay contact. When the signal on Channel 2 goes high the relay contact opens to disconnect the MP6540 from the 24V Supply voltage to simulate an opening door contact.

Channel 1 shows the supply voltage of the MP6540 which gets decreased by load current. We detect the situation and switch of the drive. When we try to restart the drive the MP6540 does not operate. There a only two ways to get the driver back to life:

  1. Cycle the Sleep-Pin (High-Low-High) or
  2. Repower the 24V-Supply voltage e.q. activating the UVLO (<4,2V).

I can only place one graphics file so I must open new topic because there a some restrictions to my user account.

Regards

Frank

4

Hello again Frank,

You should be able to upload more photos now. If you are unable to upload anything else, please upload photos as a file.

Please check if there is some sort of fault condition occurring. Here are a few places that are worth looking if this is the case:

  • The MP6540 has a UVLO threshold where if the supply dips below 4.2V based on your message, the IC may enter a latch-off state that requires a full power cycle or toggling the sleep pin to recover. Channel 1 of the oscilloscope drops significantly which may be triggering UVLO.

  • Please check the nFAULT and EN pins after this voltage drop. Please see page 12 of the MP6540 datasheet to read more on the UVLO, OCP, and Thermal Shutdown conditions which would be indicative of the nFAULT pin being logic low.

  • If the relay introducing the power drop is too slow or is causing some sort of transient spike, consider adding a bulk capacitance to smooth out the supply voltage.

  • If the MP6540 doesn’t restart after power is restored, it may not be getting a proper enable signal. Channel 2 shows PWM switching so I would think that this is unlikely but worth checking.

Hopefully this provides some insight and proves to be effective during your debugging process.

Best,
Krishan