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OMAP35xx hard reset functionality

burchmere
Intellectual 930 points
Other Parts Discussed in Thread: TPS65920, OMAP3530, OMAP3503, TPS65930

Our system uses the OMAP3530 and PMIC TPS65920.  We have need to provide a user push button switch to reset the OMAP.  We’ve tried two configurations, and neither has worked.

 

1)      Connected the push button to OMAP SYS_nRESPWRON .  When we press the reset button and ground SYS_nRESPWRON, the OMAP drives SYS_CLKREQ low to the PMIC and the PMIC stops providing HFCLKOUT to OMAP.  That is expected.  When the reset button is released, OMAP drives SYS_CLKREQ high, but PMIC never again drives out HFCLKOUT.

 

2)      Connected the push button to OMAP SYS_nRESWARM .  After pressing the reset button and then releasing, the OMAP goes into an infinite loop where it drives SYS_nRESWARM low for about 0.5 msec, once every 7 msec.

 

The PMIC to OMAP connection is:

 

PMIC                                     OMAP

nRESPWRON                      SYS_nRESPWRON

nRESWARM                        SYS_nRESWARM

INT1                                       SYS_nIRQ

nSLEEP1                               SYS_OFF_MODE

CLKREQ                                SYS_CLKREQ

HFCLKIN – from free running 26 MHz oscillator

HFCLKOUT                          SYS_XTALIN

 

Any insight as to how to properly implement a hard reset would be appreciated.

Thanks,

twebb

 

  • 0
    Intellectual 275 points

    Please let me know how this works out as I am too designing a OMAP3503 and a TPS65920 system.

     

    Below is about situation number 1.  

    Reading through the TRM for the TPS65920 it seems that you have to check your power management sequence setup to see what sequence CLKREQ activates.  Fortunately and unfortunately the part has a ton of flexibility which allows a lot of control of the part but with that comes a lot of ways to mess things up.  I would first see if you can remove the connection between the OMAP SYS_CLKREQ and the PMIC CLKREQ and pull that the PMIC CLKREQ high and see if that fixes your problem.  If it does than it's probably the sequence programming that has to be setup correct.  Also what happens on the SYS_OFF_MODE signal in this case as the nSLEEP1 signal also controls a number of things inside the PMIC.  This is also programmable.

    Another questions is do you have an open collector buffer between the output of RESPWRON from the TPS65920 and the OMAP.  The RESPWRON from the TPS65920 is not an open collector output so grounding that pin directly is not the best idea.

     

    Let me know what happens.

  • 0 in reply to gge
    Intellectual 390 points

    Dear All,

    We are also designing the board using OMAP3530+TPS65930.

    Here we are supervising the power and generating the resetout from supervisory chip.

    My doubt is where to connect this reset out?

    Whether i need to connect to power on reset input  pin or warm reset input of OMAP3530?

    As well as i am planning to give hard reset push button switch. so please let me know how to proceed?

    Please share your ideas.

    Regards,

    Murugan.M