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DRV8889-Q1: DRV8889-Q1: VREF at IFS

Part Number: DRV8889-Q1
Other Parts Discussed in Thread: DRV8452, DRV8434S

Tool/software:

Hello everybody,

I want to drive the motor driver at Full Scale Current of 1,5A, so the VREF needs to be 3,3V and TRQ_DAC = 100% (according to formula on page 20).

In section "absolute maximum ratings" is written the pin can be driven with Vmax = 5,75V, but in Datasheet in table "Pin Fuctions" on page 4 is written that you can connect a maximum of 3,3V.

I will connect the pin with a voltage divider and to have the IFS = 1,5A the voltage is slightly higher as 3,3V (about 3,5V) to reach maximum current.

So the question is, if this is acceptable?

Best regards,

Alex

  • Hi Alex,

    The recommended operating conditions specification for the VREF pin is 0.05 to 3.3 V. TI recommendation is not to exceed these operating conditions. 

    The absolute maximum ratings is the voltage specification at which this pin is permanently damaged. So a 3.5 V input to VREF will likely not damage the device. However, it does not guarantee proper device operation. For proper device operation VREF must be ≤ 3.3 V.

    That said, just because the maximum current supported by device is 1.5 A does not mean it can be used at the maximum current drive in any application. Power dissipation will play an important role as well as the ambient temperature TA of the application, the package variant of the DRV8889-Q1 - see RθJA Junction-to-ambient thermal resistance specifications, VM voltage etc. Please review the section 8.2.4 Thermal Application starting from page-60 of the datasheet. Using this formulae you can estimate the die temperature for your application. If the temperature exceeds the TSD thermal shutdown limit the device cannot be used to drive that level of current. For driving 1.5 A full-scale current IFS with a good safety margin for thermal performance, you may have to consider the DRV8434S, DRV8452S, DRV8452 DDW etc. Thank you.

    Regards, Murugavel