DRV8874: Stop motor by sensing current (DRV8874)

Jose Ramon Hernandez

Part Number: DRV8874
Other Parts Discussed in Thread: DRV8847, DRV8850

Hello,

I am working in a low voltage solution (3V) for opening/closing lockers by driving a BDC motor (forward/reverse).

For detecting the end of the lock/unlock process I could do it by timeout, but this may show problems across different systems/motors/tolerances. So, I would like to use current sensing in order to know when to stop the motor. Note the motor will draw more current when reaching mechanical limit of the locker.

¿Does this approach make sense for you?

I have seen the Isense is used for limiting the current at start-up, but not for stopping the motor when reaching a limit. This will happen if the over-current limit ("Iocp") is overpassed as protection.

Is there anyway to perform this technique by using nFAULT, TRQ signals and Rsense? Or should I use instead an external ADC for measuring the voltage across a shunt resistor in series with the motor? In this case do you recommend to connect the shunt to Isense pin?

Regards, Ramon.

over 5 years ago

0 Wang5577 over 5 years ago

TI__Guru 56650 points

Ramon,

The

IPROPI current-sense output allows a microcontroller to detect motor stall or changes in load conditions. You don't need an external ADC to measure the current across the shunt resistor. You can use a comparator to monitor IPROPI pin voltage.

0 Jose Ramon Hernandez over 5 years ago in reply to Wang5577

Prodigy 40 points

Hi Wang,

Thanks for the answer.

I am afraid the DRV8847 has no IPROPI pin.

I hace chosen this part beacause I want to handle motor/solenoid with the lowest voltaged possible (3V / 3,3V). I think this part does not support curretn sensing.

Reagrds, Ramon.

0 Wang5577 over 5 years ago in reply to Jose Ramon Hernandez

TI__Guru 56650 points

Ramon,

Yes. DRV8847 doesn't have IPROPI pin. For those low voltage device, you may consider TLV2371IDBVR OPAMP to get a similar function.

0 Jose Ramon Hernandez over 5 years ago in reply to Wang5577

Prodigy 40 points

Hello Wang,

Thanks for your comments.

If I want to avoid adding an OpAmp I think I might use the DRV8850 I think it meets my requirements:

- Vmin = 3,3 V

- Load: DC motor and/or solenoid.

¿What do you think?

I think the DRV8850 has no current regulation, but I am not sure in which cases the current regulation is needed or recommended. Could you clarify this?

Regards, Ramon.

0 Wang5577 over 5 years ago in reply to Jose Ramon Hernandez

TI__Guru 56650 points

Ramon,

DRV8850 seems work. If the customer want to control the speed or the motor torque they may need the current regulation function.

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DRV8874: Stop motor by sensing current (DRV8874)