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TUSS4470: Low Power

Edoardo Testolin
Prodigy 110 points
Part Number: TUSS4470

Tool/software:

Hi,

I want to design a radio battery ultrasonic sensor using TUSS4470, so the main issue is low power.

The idea is to power on (via a mosfet) the chip, take the measure and shut down.

The datasheet states 10ms before the chip can accept  any SPI command. Unfortunately current consumption during this phase is 11.5 mA, too high.

But I found that after 1ms of power on if I send a sleep or standby command this is accepted and current consumption goes down according to the power mode selected (220uA/1.5mA).

So why datasheet says 10ms? Ok it's a max value, but from 1 to 10ms the time is long.

Thank you and best regards

  • 0
    TI__Mastermind 43970 points

    Hello Edoardo,

    As you mention, the datasheet value is a maximum.  The maximum value is set to ensure that all devices across all lots and future lots can meet this specification.  We guarantee that the device will meet the maximum spec, but we cannot guarantee timing that is outside of the datasheet spec.     

  • 0
    Prodigy 110 points

    That's ok, but I tested other 6 TUSS with the same 1ms of startup time. Probably all belonging to the same lot, a lucky lot!. Or more probably 10ms is an overestimated value. Anyway, if I write the sleep flag and then I read the same value can I suppose the chip is ready? Do I have to wait anoother 9ms to start operations?

    Thank you

  • 0 in reply to Edoardo Testolin
    TI__Mastermind 43970 points

    Edoardo,

    I tend to agree that the spec seems a bit higher than expected, so I looked at the internal test data that we have for this specification.  From the test data, it appears that the longer wait times are related to lower VDD(less than 3.3V).

    For your application, if you are using 3.3V or 5V supply, and able to write and read back the sleep flag, you can assume the chip is ready for communication and do not need to wait another 9ms.    

    Hope this helps!

  • 0 in reply to Eddie LaCost
    Prodigy 110 points

    Hi Eddie,

    that's good, in my application VDD is 3.3V.

    Thank you so much