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MCF8315C-Q1: MCF8315C current measure value not equal to the configured value.

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Prodigy 20 points
Part Number: MCF8315C-Q1
Other Parts Discussed in Thread: MCF8315C

MCF8315C current measure value not equal to the configured value.

Hello, I used MCF8315C to control BLDC. I configure current by writting register, and measure it by oscilloscope。

But I find the measure value doesn't equal to the configured value, and they have a const rate. Why?

1) MOTOR_STARTUP1.ALIGN_OR_SLOW_CURRENT_ILIMIT

    a. set value=250mA, measure value=164mA.  250/164=1.524.

    b. set value=500mA, measure value=324mA.  500/324=1.543.

2) MOTOR_STARTUP2.OL_ILIMIT

    a. set value=250mA, measure value=160mA.  250/160=1.5625.

    b. set value=500mA, measure value=336mA.  500/336=1.602.

  • 0
    TI__Expert 8840 points

    Hi,

    Could you please let me know what GUI and which version you are using?

    With the ratio that you are measuring, I suspect that this is due an error in the GUI version that you are using, where the dropdown options of the current limit control widgets were not updated properly.

    If you look at the current limit options in the MCF8315C datasheet, there are no 250mA or 500mA options:

    Whereas the MCF8316C datasheet options have those options:

    The current limits on the MCF8315 are scaled down by a factor of 5/8 from the MCF8316. This is very similar to the ratio that you observed.

    Regards,
    Eric C.

  • 0 in reply to Eric Chen
    Prodigy 20 points

    Hi,

    Thanks. I have find the reason. I have been using old datasheet (SLLSFV6-MAY 2023), which the configure data are wrong. I will download the newest datasheet (SLLSFV6-JANUARY 2024) and check all registers data.