DRV8873HEVM: How to use the current monitoring function?

Hey Wenjuan,

Great question! 

First, OCP is a separate feature than current sense/regulation.  OCP is built into each FET of the device, and is a protection circuit that will trip to protect the device.  This OCP trip level is not (typically) adjustable. 

Current sensing/regulation is the feature built into the device that will turn the output FET on/off to limit the current at a given level.  Keep reading in the datasheet a couple of pages beyond the screenshot you sent - 

^That diagram shows the current being regulated - it will detect it crossing the trip point, turn off the output for a bit, turn the output back on until it crosses the trip point, turn off, etc etc.

OCP will come into play if the current rises fast enough that the ITRIP doesn't detect it before it crosses the OCP limit of the FET.  This often happens in the case of a dead short between OUTx and GND or VM.  

Best,

Jacob

Hi Jacob,

Thank you for your answer.
I have understood about the the OCP and Drive Current settings.
But I have another question, as the screenshot you sent me shows, the setting for monitoring current is actually the setting for Itrip.
But Itrip is only for PWM mode. If I use PH/EN mode or independent half bridge mode,what is the purpose of the current monitoring function?

Looking forward to your reply.

Wenjuan

Hey Wenjuan,

The current regulation will work in any of the control modes - PWM, PH/EN, or independent mode.  (Note that the current sensing occurs in the high-side FET, so if current is only flowing through the Low-Side FET then the current regulation/sensing won't work at that time) 

PWM or PH/EN is just the input control mode - the device will still implement this on/off cycle on the output of the device automatically to maintain current.

Best,

Jacob

Hi Jacob,

Thank you for your answer.

Since I am planning to use the hardware-interface device, as in the part of my screenshot, the ITRIP is fixed at 6.5A, how should I understand it?

Is it possible to use THE CURRENT REGULATION to adjust the current value of Itrip?

Looking forward to your reply.

Wenjuan

Hey Wenjuan,

Not with this device.

If this is a new design would you be interested in a different motor driver such as DRV8256 or DRV8262?  DRV8873 is a fairly old device and these devices will give you better performance for size/cost. 

Best,

Jacob 

Hi Jacob,

I have understood and thank you for your reply.

Best,

Wenjuan