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DRV8889-Q1: how to understand the tutw spec

Colt Zhang
Expert 4985 points
Part Number: DRV8889-Q1

Tool/software:

hi expert,

my customer use DRV8889-Q1, when the temp is just up to -10℃， the DRV8889-Q1 will report the Undertemperature warning.in our data sheet, we have a spec Tutw, but why this threshold is not a fixed value, this spec have min and max and type value, so how to understand the spec. 

another question, how to detect and implement the under temperature warning in our DRV8889-Q1

  • 0
    TI__Mastermind 44465 points

    Hi Colt,

    Colt Zhang said:
    in our data sheet, we have a spec Tutw, but why this threshold is not a fixed value, this spec have min and max and type value, so how to understand the spec. 

    This specification covers device to device variation across production lots, operating voltage range etc. and has 6-sigma boundaries. This means some devices may report UTW at 5°C and some could report at - 25°C - error range spread. But most devices could be centered around the typical value of -10°C. 

    Colt Zhang said:
    another question, how to detect and implement the under temperature warning in our DRV8889-Q1

    This is described in the below section of the datasheet. The UTW is a report only function, reports to the ECU when the die temperature is < TUTW. The TW_REP bit determines whether this reporting pulls nFAULT low or not. Low temperature is automatically detected by the device with the on-chip temperature sensor. It is not possible to calibrate this temperature sensor hence the variation MIN and MAX specification of the TUTW.  Thanks.

    Regards, Murugavel 

  • 0
    Prodigy 40 points

    The customer has doubts about the range of low temperature warning, which can be reported from 5 ℃ to -25 ℃. The entire range is 30 ℃. We would like to know under whatscenarios such a wide temperature range design will be used. We understand that the significance of this large range is not significant and would like to know more. And the working temperature of the chip is -40 ℃, why does it report at -25 ℃? Will there be any problems when it reaches -40 ℃? 

  • 0 in reply to qiang lin
    TI__Mastermind 44465 points

    Hi Qiang,

    qiang lin said:
    The customer has doubts about the range of low temperature warning, which can be reported from 5 ℃ to -25 ℃. The entire range is 30 ℃.

    The on-chip temperature sensor is a coarse sensor meaning not finely calibrated - not possible for every device. The variation covers device to device and lot to lot in production over time mostly centered around the -10C TYP value. -25C MIN and 5 MAX are the top and bottom end corner cases with 6-sigma limits.

    qiang lin said:
    Will there be any problems when it reaches -40 ℃? 

    The operating range of the device is -40 ℃ to 125 ℃ TA. This has been qualified as per AEC qual standards. We have validated the device for this entire operating temperature range and found it compliant. No issues anticipated withing this operating TA range. Thank you.

    Regards, Murugavel 

  • 0 in reply to Murugavel4637
    Prodigy 40 points

    Can you tell me the original intention of this design(low temperature warning)

  • 0 in reply to qiang lin
    TI__Mastermind 44465 points

    Hi Qiang,

    Some stepper motor mechanical assembly do not function at low temperatures due to increased friction and/or jammed lubricants. The UTW sensing provides a feedback to the ECU that the temperature is low and ECU could make a decision to not drive the motor assembly under this condition. Thanks.

    Regards, Murugavel