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DRV8305: Having failures appears to be related to over heating.

Scott Morrill
Prodigy 60 points
Part Number: DRV8305
Other Parts Discussed in Thread: TMS320F28027F

We are using Insta-SPIN motor-ware and the DRV8305 with the TMS320F28027F much like the development board, in fact there are very few hardware changes.  We are experiencing failed units in the field, it is always the DRV8305 that has failed, with the O-Scope I find that all gate-drive signals are missing even when input signals are active and gate-drive is enabled.  SPI is working.

The DRV8305 case temperature can be as hot as 90degC when ambient is 25degC, the failures seem to coincide with ambient temperatures above 30degC.  The DRV8305 measures hotter than the MosFETS.

I'll be honest that I don't understand how the DRV8305 can be so hot, even at ZERO speed the DRV8305 case temp is 70degC.

Gate Drive sink and source currents are set to default 50mA.

PWM freq is 90KHz

We are driving a very low inductance FAN, we command velocities from 0 to 30KRPM:

#elif (USER_MOTOR == Grabit_Fan_Motor_Large_V2)
#define USER_MOTOR_TYPE                 MOTOR_Type_Pm
#define USER_MOTOR_NUM_POLE_PAIRS       (3)
#define USER_MOTOR_Rr                   (NULL)
#define USER_MOTOR_Rs                   0.0075 //(0.0133)
#define USER_MOTOR_Ls_d                 0.0000012//(0.0000006)
#define USER_MOTOR_Ls_q                 0.0000012 //(0.0000006)
#define USER_MOTOR_RATED_FLUX           (0.0014)
#define USER_MOTOR_MAGNETIZING_CURRENT  (NULL)
#define USER_MOTOR_RES_EST_CURRENT      (12)
#define USER_MOTOR_IND_EST_CURRENT      (-16.0)
#define USER_MOTOR_MAX_CURRENT          (24.0)  //(24)
#define USER_MOTOR_FLUX_EST_FREQ_Hz     (300.0)
#undef  USER_MAX_ACCEL_Hzps
#define USER_MAX_ACCEL_Hzps             (20.0)      // 80krpm/second
#undef USER_IQ_FULL_SCALE_VOLTAGE_V
#define USER_IQ_FULL_SCALE_VOLTAGE_V (12.0)

Any advice appreciated, presently trying different heatsink approaches.

  • 0
    TI__Guru** 114905 points
    Hi Scott,

    Assuming zero current means the FETs are disabled or all three low sides are active, the device should not be this hot.

    At zero speed, what are the inputs?
    What is the VM voltage?
    What version of the DRV8305 are you using (83053, 83055, or 8305N)?
    Have you checked all the inputs and outputs to confirm they are correct?
    Do you have a second board (or an evaluation board) to confirm the behavior?

    Additional steps:
    Can you measure the current through the system as you slowly enable the DRV8305?
    After power up VM
    After Wake rising
    After EN_GATE