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DRV8350: Low side gate driver failure

Manu Sudevan
Prodigy 90 points
Part Number: DRV8350

We are developing the BLDC Motor driver using DRV8350HRTV and are facing issues with this chip.

Even without load connected, the driver suddenly fails in between our tests. The VGLS voltage drops down from 14.5V to something below 6V. When we measure the impedance at the gate we always find that the impedance of one of the low side gate drive output(as measured from the GLX pin of the DRV8350 to ground) is too low instead of around 140k.

We have testing these with VM=15V and VDRAIN=24V (even though the maximum VDRAIN planned is 48V).

The same situation happens in  three  boards and we need your urgent support to find the root cause of this issue and to rectify the same.

I am attaching the schematics for review

DRV8350 DRIVE CIRCIUT.pdf

  • 0
    TI__Guru 65330 points

    Manu,

    Thanks for posting on the MD forum!

    Please check all three low side gates and all three SLA, SLB, SLC nodes using a scope when the motor is running in the same configuration as mentioned above, we want to check for any violations of the ABS MAX ratings that may be damaging the device.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 90 points

    Hi Adam,

    Thanks for the reply.

    We haven't tested this with actual motor yet. In fact we tested using a resistive load (8 ohms between each phases) and open load until now. 

    The waveforms at the gate drives and switch nodes looks good with out ringing at normal PWM pulses with dty adjusted from 10% to 50% 

    The driver failure was noticed , once we tried the sinusoidal commutation PWM pattern. (PWM modulated with sine wave). The driver IC is showing periodic nFAULT activity before damage happened  ( Low side driver failure - impedance measured at GLx less than 70 ohms).

    Here, we haven't set any lower limit on PWM duty cycle. Hence the minimum pulse width can fall below the TDRIVE time ( 4us for the chip), also turn-on/turn off time of MOSFETs and further below. Does this lower PWM duty cycle operation impact the driver negatively, resulting in the IC damage?

    We will update you with the waveforms soon.

    Thanks & regards,

    Manu

  • 0 in reply to Manu Sudevan
    Prodigy 90 points

    Hi Adam, 

    Any updates on the above questions on minimum PWM width applicable to DRV8350HRTV ?

    Once we set the minimum PWM width to 2us, we haven't experienced the DRV8350 failure till now.

    Thanks & regards,

    Manu

  • 0 in reply to Manu Sudevan
    TI__Guru 65330 points

    Manu,

    Did this issue get resolved?

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 90 points

    Hi Adam,

    Seems like the issue got resolved, once we reduced the IDRIVE setting.

    We are testing  the driver using the actual 1KW motor and FOC algorithm.

    Regards,

    Manu