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DRV8312: DRV8312- OC_ADJ current limitin

denizdeniz
Prodigy 100 points
Part Number: DRV8312
Other Parts Discussed in Thread: DRV10974, DRV8323

I am using DRV8312 to drive 3 phase BLDC motor. BLDC motor rating is 1 A . I want to use DRV8312 Cycle by Cycle current limiting function  so limiting the current 280 mA or lower value. 

Table 2 does not show the resistör value for current lower than 1.4 A. According to table 2 of the drv8312 datasheet there is a inverse proportion between current and oc-adj resistor value . So ı put 1 M Resistör to limit current 280 mA (200*1.4/1000). 

However drv8312 limiting the curretn 20 mA or lower. Even ı put 681K Resistör drv 8312 limiting current 20 mA and lower so motor shaking but does not run. If I put 510K or lower value resistör DRV8312 run without problem at 100mA  but this time I couldnt limit the current. 

Why I couldt limit the current according to table? Is there any current threshold or something ? May be DRV8312 does not run with  higher oc_adj resistor value? 

  • 0
    TI__Mastermind 18900 points

    Hello Denizdeniz,

    Thanks for posting on the motor drive forum! Let me get back to you tomorrow with an answer.

    Best,

    -Cole

  • 0
    TI__Mastermind 18900 points

    Hello Denizdeniz,

    Unfortunately, any value resistor outside of the 22 kOhm - 200 kOhm table is not recommended (see below) and could cause unexpected behavior, like you've seen on the bench. While I am surprised that 500 kOhm worked for you, the more important distinction is that the DRV8312 was not designed for use with a motor that will consume such a small current. 

    Perhaps we can recommend an alternative part to better suit your needs? 

    • Unfortunately we don't have another integrated FET + Gate drive part with lower current limits
    • If integrated FET is a key factor, the DRV10974 might be able to . Be sure the check the input or motor voltage requirements as the part is designed with lower currents in mind
    • If you don't mind picking your own FETs for the inverter or H-bridge and doing some math between the shunt current sense resistor, current sense gain, and SEN_OCP thresholds ; we offer plenty of gate drivers with integrated current sense that could be configurable for your application. I suggest looking at the DRV8323 to start 

    Best,

    -Cole