Other Parts Discussed in Thread: TIDA-00774, ASH
Moving DRV8323H schematic review email discussion onto e2e for support.
We are evaluating DRV8323H gate driver to be used in our BLDC motor controller module. First, we got and played with a couple of BOOSTXL-DRV8323RH. That went smoothly. Now, we are testing it on our own prototype board with the more powerful MOSFETs. On the multiple boards, the DRV8323H has been blowing out suddenly. Schematic shared offline.
Also I would like to find out if is allowed to swap the SPx and SNx pins in order to have positive amplifying network gain.
Product line response: Yes, you can flip the SPx and SNx.
Questions regarding the design:
How much current load is there and how much current is expected?
Customer: 15Amax continues
I see Vds monitoring is off (3v3 to VDS pin).
Customer: Yes, this has been done intentionally. Is there any problem with doing that?
Situations, where the DRV can blow up, can be due to voltages being outside of device ratings. The device, per se, does not see currents.
Customer: We have measured voltage levels on all PWR and control pins to make sure they are correct.
If possible, please ask for an image of where the blow occurs to know what pins it stems from.
Customer: We can send an image, but it won’t be showing anything. There is no visible damage on the IC. After the DRV8323H is damaged the gate driver’s outputs are always 0V while the PWM is present on the inputs.
Is there a fault asserting before the blow?
Customer: We are still investigating this matter, but so there is not a fault asserting detected before the blow.
SPx and SNx can be flipped, although it will cause the low side VDS monitoring to include the sense resistor voltage.
Customer: If the VDS monitoring is disable, would it be safe to flip the SPx and SNx to have positive amplification gain?
Has the DRV operated successfully lower IDRIVE values?
Customer: We tried minimum configuration of IDRIVE (10/20mA). The gate signals were destroyed. This might be because our PWM frequency is 30kHz due to the low inductance (0.3mH) of the motor. 60/120mA IDRIVE and 0.26V VDS are the latest configuration that we are using.
15A max continuous expected? Is that the current seen?
Customer: A motor under test is 250W nominal power at 36V. Although it should be 7A we measured up to 16A maximum continues current while the motor was under extreme load.
Product line recommendation:
I wanted to point out that, since the customer is utilizing parallel FETs in their design, we have seen design issues before with improper circuit configuration with parallel FETs. The customer can use the following TIDA-00774 as a reference to parallel FET system design. The Design Guide’s section 6.2.1 goes into detail as to what to consider when designing parallel FET applications.
Of note are the gate resistors added to each parallel FET and the placements of these resistors, the decoupling capacitors, the power layout copper pours, and the FETs.
This post has been shared with the customer to continue the schematic review discussion here.
