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TiWi (WL1271) power up sequence

Christopher Hofmeister
Prodigy 110 points
Other Parts Discussed in Thread: WL1271

Hello,

The TiWi & WL1271 datasheet shows a power up sequence that is to be followed.  (See page 15 of http://www.lsr.com/downloads/tiwi_r2/TiWi_R2_Datasheet.pdf).  The diagram shows Vbat rising before Vio, but there is no mention of this in the text, no timing information.  Does there really need to be a delay between the two power supplies?  If so can you quantify what sort of delay there should be (uS or mS)?  

Thanks for the help.

Christopher Hofmeister

  • 0
    TI__Intellectual 1505 points

    Hello Christopher ,

     

    In the wake up sequence the decision point should be taken on the EN time frame.

     

    VBAT, VIO and SLOWCLK must be available and stable before WL_EN pin is asserted.

     

    Please note that no signals are allowed on the IO pins if no IO power supplied, because the IOs are not 'fail safe'.

     

    Exceptions are CLK_REQ_OUT, SLOWCLK, XTALP and AUD_xxx, which are failsafe and can tolerate external voltages with no VDDS.

     

    Best Regards,

    Moshe

     

     

     

  • 0 in reply to Moshe Meir
    Prodigy 170 points

    Hi,

    According to the third line of the timing diagram, WL_EN, BT_EN and FM_EN are to be pulsed high for a minimun of 10mS(328 SC cycles) after Vbat, Vio and SC are stable, then they must remain low for a minimum of 64uS(3 SC cycles).  I have a few questions:

    • Are the pulses on enable lines required?
    • The 5th line of the timing diagram shows WL_EN to be held low which conflicts with line 3 of the timing diagram.  Does line 3 show the power up sequence, then line 5 show the timing for using the radio?
    • Are these to all be pulsed at the same time, or sequentially?

    • If any of the WL, FM or BT radios are not used, must we still pulse those enables ?

    • Vbat, Vio and SC will be stable for some time before the enables are pulsed.  What state is the radio in prior to pulsing the enables?

    • May any of the radios be enabled for use immediately after the 64uS window mentioned above?

      Best Regards,

    Matt