DRV8701: Question on current recirculation in half bridge mode

Alvin Zheng

Part Number: DRV8701

Hi, Team

I got report that in half bridge mode of DRV8701, during motor decelerate, current recirculates back to VM and lift VM up.

According to spec, in half bridge mode, current recirculate only on low side as slow decay.

Here attached waveforms:

CH1: Low Side MOS current (SH->GND as positive)

CH2: GL2

CH3: GH2

over 6 years ago

0 Alvin Zheng over 6 years ago

TI__Intellectual 900 points

When using Diodes to replace the low side MOS, the issue disappear. Wonder that is allow for DRV8701?

Waveforms attached.

CH1: Motor current

CH2: GH2

CH3: EN

0 Alvin Zheng over 6 years ago in reply to Alvin Zheng

TI__Intellectual 900 points

Here attaches voltage on SH2.

Normal operation: 24.1V

Issue happens: 25.8V (Higher than power supply which is 24V)

0 Rick Duncan over 6 years ago in reply to Alvin Zheng

TI__Guru** 114905 points

Hi Alvin,

We will investigate and reply soon.

0 Rick Duncan over 6 years ago in reply to Rick Duncan

TI__Guru** 114905 points

Hi Alvin,

We have evaluated this scenario in our lab and have not been able to duplicate this situation. Would you provide additional details, such as scope captures of the SH2, SP, and VM voltages when decelerating the motor?

0 Alvin Zheng over 6 years ago in reply to Rick Duncan

TI__Intellectual 900 points

Hi, Rick

Customer did test on EVM. Waveform shows VM is raised. So there should be current back to VM from some path.

Attached the waveform. And schematics of EVM with modification by customer (in red, R12 R21, R22, R29 NC.)电气连接示意图.pdf

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DRV8701: Question on current recirculation in half bridge mode