Part Number:DRV8701
We would like to use the DRV8701 as an alternative to a currently used discrete circuit. However, we found the following significant problem in the test setup. In the de-energized phase of PWM we leave the high side MOSFET switched on in our discrete configuration. The DRV-chip switches off the bridge completely. In our discrete circuitry, a certain motor type starts reliably under identical conditions with a duty cycle of approx. 20% (33kHz clock frequency). The DRV chip must output a duty cycle of approx. 70% under otherwise identical conditions. In the meantime, we have found that this is due to the fact that the high MOSFET, which is switched off by the DRV-chip, converts the counter-EMK completely into a braking effect.
What proposal does TI have to avoid this problem? We have to control the engine. However, a controller then only has the difference of 70% to 100% duty cycle available as a control interval. I look forward to receiving a more detailed answer.
F. Giesen
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