DRV8844: Full bridge configuration

matt schumann

Part Number: DRV8844

Connected the dev board DRV8844EVM to my control outputs; 2 direction lines and one PWM output.

I connected output 1 and 2 on one side of the motor and output 3 and 4 on the other side.

I then connected the control pins based on the Table 2 in the data sheet for fast decay.

Connected IN1 and IN2 to one control line, connected IN3 and IN4 to other control line and connected the PWM to EN1, EN2, EN3 and EN4.

There is PWM output but not motor movement. So I am assuming I have the bridge or pin configuration incorrect.

Please let me know the best setup for a single DC motor.

Thanks - Matt

over 4 years ago

0 Hector Hernandez Luque over 4 years ago

TI__Expert 8980 points

Hi Matt,

The best setup depends on what you are trying to do.

If you are trying to drive a single DC motor in both directions and using slow decay, then you need to connect the motor to OUT1/OUT2, your PWM to EN1/EN2, and your Control logic to IN1/IN2.

Make sure nRESET and nSLEEP are both logic high.

If you are utilizing your own microcontroller and not the EVM onboard MCU, please remove the highlighter jumpers found in the image below and make sure you provide corresponding jumper signals from your board (e.g. INx, ENx, nRESET, nSLEEP).

Make sure your VM is above the minimum voltage and enough to drive your load.

What PWM frequency and duty cycle are you operating at?

Let me know if you have any issues here or if the issue still persists.

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

Prodigy 30 points

Thank you for the information. I did remove the jumpers to use my circuit board.

I am trying to utilize the full 5A capability for one motor. Is this possible?

I have it configured as:

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

TI__Expert 8980 points

Hi Matt,

I did not notice you were paralleling your outputs, thank you for referencing it again in the image.

Your pin configuration appears correct and you should be able to drive that current capability with this device, assuming that when you say you see PWM output you mean you see output voltage on the OUTx pins.

Did you compare your input logic with your output logic, and verify the outputs behave as expected?

What PWM frequency and duty cycle are you operating at?

Can you share your motor's information?

Are you grounding or using a sense resistor on SRC12 and SRC34?

What VM voltage are you utilizing?

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

TI__Expert 8980 points

Actually, I can get most of that information with scope capture. :)

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

Prodigy 30 points

Hector

I am running the PWM at 24KHz.

The motor is a 24VDC motor

The system is running at 24V.

Here is a pic of how I have the dev board configured.

Scope plot showing outputs with motor not connected.

With motor connected.

It seems like I am missing something simple.

Thanks,

Matt

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

TI__Expert 8980 points

Hi Matt,

Thank you for the scope captures. While I study these captures and think some more, can you share the motor specifications and part number?

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

TI__Expert 8980 points

Hi Matt,

Alright, theory time:

It seems you are utilizing fast decay, and not enough torque is being generated to drive the motor by the time it has de-energized. Two possible trials to verify this: increase the duty cycle or utilize slow decay (better route). Utilizing slow decay, it would require that you PWM the INx signals instead of the ENx signals.

Please, let me know how your trials go and if you have any more questions.

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

TI__Expert 8980 points

Hi Matt,

Any updates here? Please, keep me informed of any new developments. Thank you.

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

TI__Expert 8980 points

Hi Matt,

Closing the thread for now. Please, feel free to respond by replying to this thread or opening a new thread in our forum. Thank you.

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DRV8844: Full bridge configuration