Motor driver with integrated current control

Philipp Overath

Other Parts Discussed in Thread: DRV8870, DRV8871, DRV8885

Good Day, we are looking for driving Brushed DC Motors (24V currently, but would work with 12V). The Motor will have currents up to 800mA. The Driver should have internal current control. Is there such an TI Driver?

Thank you very much

over 7 years ago

0 Matt Hein over 7 years ago

TI__Mastermind 21805 points

Hello Philipp,

We have several options for you to consider: DRV8870 would be the easiest solution at only 8 pins.

Check here for a bigger list of devices that can meet your requirements: LINK

Thanks,

Matt

0 Philipp Overath over 7 years ago in reply to Matt Hein

Prodigy 140 points

Thanks for the quick reply.
As I see it the DRV8870 just outputs the current as a voltage over a resistor, right? So it has no internal current control?

Thanks

0 Philipp Overath over 7 years ago in reply to Philipp Overath

Prodigy 140 points

One more question. What exactly does 'current regulation' mean. Is this equivalent to current control?

0 Matt Hein over 7 years ago in reply to Philipp Overath

TI__Mastermind 21805 points

Hi Philipp,

DRV8871 is a device similar to DRV8870, except with an integrated sense resistor.

Thanks,
Matt

0 Matt Hein over 7 years ago in reply to Philipp Overath

TI__Mastermind 21805 points

Hello Philipp,

Current regulation is a method of current control in which a PWM is applied to the motor to regulate current with some ripple in a very efficient way (instead of with a linear driver which causes a lot of power dissipation).

Thanks,
Matt

0 Philipp Overath over 7 years ago in reply to Matt Hein

Prodigy 140 points

Thanks for the reply. But it is only for regulating the current, not for dynamic control of it, right?

0 Rick Duncan over 7 years ago in reply to Philipp Overath

TI__Guru** 114905 points

Hi Philipp,

Yes, it is typically only for regulating the current but can be used to dynamically control the current.

If you want to dynamically control the current, the VREF input can be changed dynamically.

0 Philipp Overath over 7 years ago in reply to Rick Duncan

Prodigy 140 points

And how do u change the vref inpuf dynamically?
Thanks

0 Rick Duncan over 7 years ago in reply to Philipp Overath

TI__Guru** 114905 points

Hi Philipp,

Please refer to Figures 15 and 16 of the DRV8885 datasheet as an example of how to control the DRV8871 (DRV8885 RREF is similar to DRV8871 ILIM).

For the DRV8870, the VREF can be controlled by a DAC, PWM, or switching resistors in and out.

0 Philipp Overath over 7 years ago in reply to Rick Duncan

Prodigy 140 points

Thanks,
so DRV8870 and DRV8871 only differ that one has Current Regulation and the other Integrated Current Sensing, right? Which would be best fit for dynamic control of the current?

Thanks

0 Rick Duncan over 7 years ago in reply to Philipp Overath

TI__Guru** 114905 points

Both the DRV8870 and DRV8871 regulate current. Both are good at dynamic control of current. It really depends on your preferred components around the device.

The current control circuitry is different between the two.
The DRV8870 requires a VREF voltage and external sense resistor.
The DRV8871 requires a small resistor to from ILIM to GND.

For maximum flexibility of dynamic current control, modifying a voltage at VREF or at the bottom of the ILIM resistor instead of a connection to GND is needed.

If there are two current settings, a switch to change the VREF voltage or change the ILIM resistor value can be used.

0 Hector Hernandez Luque over 7 years ago in reply to Rick Duncan

TI__Expert 8985 points

Hi Phillip,

Did Rick's suggestion resolve your question?

If so, please close this post by accepting the post is resolved in Rick's highlighted in yellow answer above me.

Thanks!

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