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DRV8873: ITRIP regulation and RIPROPI resistor selection

Part Number: DRV8873
Other Parts Discussed in Thread: DRV8245-Q1,

1) In [6.5] the datasheet lists possible ITRIP values as 3.85, 5.4, 6.5, 7A. However in [7.3.1.3, Table 8] the values are 4, 5.4, 6.5, 7A. Which one is correct?

2) In DRV8245-Q1 datasheet [8.3.3.3] the schematic clearly shows that Vitrip is compared to Vipropi, which means the actual trip current depends on external Ripropi resistor. Furthermore, in Table 8-10 the trip level is expressed in Vitrip voltage, which makes perfect sense and allows fine-tuning ITRIP level by selecting suitable Ripropi resistor value.

In DRV8873 datasheet [Table 8] gives ITRIP limits in absolute values, which implies they do not depend on Ripropi resistor. How does current limit work in DRV8873? Is there another fixed internal resistor?

3) The note in DRV8245 datasheet says: "The user inputs always takes precedence over the internal control. That means that if the inputs change during the TOFF time, the remainder of the TOFF time is ignored and the outputs will follow the inputs as commanded."

So, if PWM pulses continue then they will cancel load regulation. Doesn't it make ITRIP feature useless?

Is the same true for DRV8873?

  • Hello,

    Today is a US holiday.  Will address your questions on Monday, 11/28.

    Regards,

    Ryan

  • Dmitry,

    1)  Please follow the EC table (6.5) as the the correct line with limits.

    2)  DRV8873 behaves differently from 8245-Q1.  ITRIP does not depend on Ripropi.  The absolute values are determined via internal selectable settings per the datasheet.

    3)  This is NOT true for the DRV8873.  Current regulation still works just fine on the DRV8245-Q1.  You just have the option to truncate a TOFF period.  If after returning to a drive state and current limit is hit again, TOFF period will again start to limit current.

    Regards,

    Ryan