• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 425 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8701: DRV8701 Hbridge looking for extra free wheeling diodes required for Emagnet

Bastiaan Pierik75
Intellectual 370 points
Part Number: DRV8701

Dear Support,

i have an interesting project.

I have 2 18V25 Hbridge from Polulu it has 4 NVMFS5C423NL N mosfets in use for the Hbridge topology.

the first HBridge with the 18V25 has a power supply 2231A-30-3 at 6A at 24V connected and is switching at 50/50 1KHz,10KHz, 100KHz with a le croy awg.

That by hookin up an Inductor (measured with LCR in Series, 18mH  internal resistance of 2Ohm) that there is a lot of inductive kick back at 1KHz,10KHz, and 100KHz.

The maximum current that should run through each coil is 8.36A without free wheel diodes as extra protection.

First Question:

which free wheel diodes would you recommend as extra protection?

Second question:

which protection matters should be taken in place on the circuit board. i have the 24V for the Emagnet connected to a dcdc converter

That bucks the 24V to 5V on which the DRV8701 and the IMXRT1062 are connected to the same ground.

I would like to protect these against negative spikes as you can see. Yellow is the PWM signal 50/50, Red is the Current through one of the Coils, and the Blue is the Kickback, I dont think the MCU is going to like these spikes.

Together with that I have a few max31855 temperature sensors which I read over SPI on it which have a nup2105 protection to GND.

I would love to have some advice on this.

best regards

Bastiaan

10KHz


third example at 100KHz

  • 0
    TI__Mastermind 37683 points

    Hi Bastiaan,

    Thank you for posting to the motor drivers forum.

    1. I suggest using Schottky diodes rated for the maximum current expected through the coils. 
    2. The DRV8701 comes with protection features like over-current protection and over-temperature shutdown that disables the H-bridge. To further protect against the voltage spikes, you can add TVS diodes or varistors across the outputs of the H-bridge to limit the voltage spikes.