DRV8850: Is VPROPI output proportional to the sum of currents in the

Nick Alexeev

Part Number: DRV8850

Hello,

I'd like to use half-bridges in the DRV8850 in parallel (OUT1 and OUT2 connected together), and connect the motor between this combined output and ground. I expect that I can drive the motor with more current that way. I only need to turn the motor in one direction. Each MOSFET in the bridge has got an individual logic control input.

I need to limit current during motor startup, or accidental stall. I'm reading 7.3.3 in the datasheet, and my question is about current sensing in DRV8850. Is the current out of the VPROPI proportional to the sum of current in the high side MOSFETs?

Best regards,
- Nick

p.s. If the pin VPROPI outputs current proportional to current flowing in the bridge, shouldn't it be called IPROPI?

over 4 years ago

0 Hector Hernandez Luque over 4 years ago

TI__Expert 8980 points

Hi Nick,

Below Figure 14 in the datasheet, you can see that is states, "During typical operation, VPROPI represents the total current flowing to loads connected to OUT1 and OUT2."

Unless specifically stated in the datasheet, it is not recommended to connect the outputs in parallel. Timing mis-matches can create events that look like shoot-through.

0 Nick Alexeev over 4 years ago in reply to Hector Hernandez Luque

Intellectual 605 points

Timing mis-matches can create events that look like shoot-through.

I'm going to generate the IN1H=IN2H, IN1L=IN2L control signals with an delay between turning off both lower MOSFETs and turn on of both upper MOSFETs [and the other way as well]. I'm open to your suggestions as to how long this delay should be. That should take care of the potential shooth-throughs, should it not?

0 Hector Hernandez Luque over 4 years ago in reply to Nick Alexeev

TI__Expert 8980 points

Hi Nick,

The timing mismatches are not measured. Testing and validation of your system and of your drive configuration are required to conclude if the design decisions are valid.

Your decision to insert a delay can potentially avoid the shoot-through.

0 Hector Hernandez Luque over 4 years ago in reply to Hector Hernandez Luque

TI__Expert 8980 points

Hi Nick,

I will close this thread for now. If you have a reply, please reply directly to this thread or open a new thread. Thank you.

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