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VREF goes low 200 mV without motor connections

ALbert Tello
Intellectual 735 points

We are have problem with drv8432 VREF goes low without any motion or motor connection

We replace a digital [pot and we put AGND a 64.9K resistor , also we added a 4.3K pull down resistor to RESET_AB and RESET_CD pin.

The problem appear when we run the software trough  a JTAG port , the DSP IO's are 3.3. V

We are facing this problem recently and we are close to be in production , 

What can be the problem that VREF goes low , , we are using a LAB power supply with protections, guarantied w no over current happen, We are in the dark here with this problem

Second Question: when Vref goes low means drv8432 burned ?

Albert

  • 0
    Intellectual 735 points

    Correction VREG instead VREF

  • 0 in reply to ALbert Tello
    TI__Guru** 114905 points

    Hi Albert

    Is this the same board as before but with a resistor for OC_ADJ instead of the digital pot? If I recall, you had 4 DRV8432 per board.

    Do all devices have a problem or just one? If it is just one, it may be a layout issue.

    Does the problem appear when running code normally and not through the JTAG? What is the code doing when running through the JTAG? Is the JTAG interfering with normal operation or slowing it down, causing this problem?

    Do you have any specific symptoms? Can you place a scope probe on VREG and capture suspect signals when VREG drops?

    We will discuss this among the team and get back with you.

  • 0 in reply to Rick Duncan
    Intellectual 735 points

    Same board with the difference a Digital pot  in series with a 64K9 Resitor.

    Here are the Electrical Spec:

    VDD, GVDDD[A,B,C,D] = 12.23 V

    VCC Digital DSP 3.3 V

    VCC OP and Digital POT =5V

    OTW, FAULT connected to micro controller directly,  NO pull resistor, (can be this the problem that when the flash is burning or or dsPIC is debugging  can be configured as output and damage VREG  )  . When VREG = 0 both are tied to 0 which make sense.

    PVDD[A,B,C,D] = 24 V, No motor connected

    M1, M2 connected to AGND , and M3 controlled by micro-controller

    VREG : 200 mV

    Description :

    After a new drv8432 is replaced all voltage are fine and VREG =3.3

    The problem occurs when we star breakpoints the program 

    Albert