DRV8343-Q1: Issue w/ waveform

Mitchell

Part Number: DRV8343-Q1

Hi Team,

My customer has a question regarding DRV8343-q1 in their motor board. They are getting an interesting output waveform on the SOA, SOB, SOC outputs. A shot of the waveform is attached along with schematic pages of the motor power stage and controller. We checked the current through the motor phases and the waveform looks normal, so only at the SOx output is it acting strange. The register commands are written below:

0x05: 0x40

0x06: 0xCC

0x07: 0xCC

0x08: 0xCC

0x09: 0x99

0x0A: 0x99

0x0B: 0x99

0x0C: 0x2C

0x0D: 0x61

0x0E: 0x00

0x0F: 0x15

0x10: 0x3F

0x11: 0x00

0x12: 0x00

Thanks,
Mitchell

over 4 years ago

0 Matt Hein over 4 years ago

TI__Mastermind 21805 points

Hi Mitchell,

I don't see the schematic, can you re-send it?

Thanks,

Matt

0 Mitchell over 4 years ago in reply to Matt Hein

TI__Expert 4915 points

Hi Matt,

Sorry about that, I will share it with you directly.

0 Matt Hein over 4 years ago in reply to Mitchell

TI__Mastermind 21805 points

Hi Mitchell,

While I review the register settings, can you have them capture SOA/TP12, SH-A/DL_A/OUT-A, GL-A, and INLA on one oscilloscope screen when the event is happening?

Also, what is the PWM MODE configured to?

Thanks,

Matt

0 Matt Hein over 4 years ago in reply to Matt Hein

TI__Mastermind 21805 points

Hi Mitchell,

The IDRIVE setting of 735mA seems awfully high for a MOSFET with QGD = 13.6nC. We normally expect 100-300ns, corresponding to an IDRIVE setting between 45 and 136mA. Maybe the 65mA setting is better suited?

Thanks,

Matt

0 Matt Hein over 4 years ago in reply to Matt Hein

TI__Mastermind 21805 points

Hi Mitchell,

Another thought I had was to observe SOA/TP12, SP-A, and SN-A on the scope. There could be voltage oscillation on the SP-A node resulting in an abnormal input to the CSA.

We do recommend having a 0.01-1uF capacitor from the drain of the high-side MOSFET to the source of the low-side MOSFET (top of the sense resistor) in order to mitigate some of the parasitic inductance from the low-side source to the ground connector on the board.

Thanks,

Matt

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DRV8343-Q1: Issue w/ waveform