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DRV8332: Data sheet question: Why recommend OC latching mode only at 13.2A

Robbie Valentine86
Expert 1550 points
Part Number: DRV8332

Hello,

I am seeing peak current pulses of about 10-11A per phase when my BLDC motor is under load.  I have the following configuration: M3=1, M2=0, M1=0.  The peak current stays at this level (stays peaking at 10-11A) for a few seconds then the motor driver shuts off and faults.  I have set my current limit to a 22k resistor (11.6A).  I know it is current related because I can re-trigger the PWM module and the driver/motor starts right up again. 

In trying to remedy this, I wanted to increase the current limit and this is where my questions stem from.

Questions:

1. Why does 13.2A (19k current resistor) require me to use OC latching mode instead of CBC mode.  This comes from Table 2. Programming-Resistor Values and OC threshold.

2. How does OC latching actually work?  As soon as there is a peak no mater how short a duration the driver will latch itself off?

3. If I'm in CBC mode is there a way for the driver to shut down?  It seems that this is happening to me.

Thanks!

  • 0
    TI__Guru 65390 points
    Robbie,

    1. Table 2 says "recommended to use OC latching mode". It's recommended because not all boards and designs can handle this higher current when it is in CBC mode. If it works for your board then it's up to you if you want to use it.

    2. In CBC mode, the device actively attempts to reduce the overcurrent for a certain "retry" period. If the current reduces before the timeout occurs, the operation resumes as normal. When in latched mode, as soon as overcurrent is detected, the system triggers an output shutdown.

    3. Yes, if the overcurrent still exists at the end of the retry period, the system enters the second protection level which is the same as the latching shutdown.

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Expert 1550 points
    Thanks Adam! Great response!