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AM335x with TPS65910A3 power up without power button

shriram
Intellectual 705 points
Other Parts Discussed in Thread: AM3359, TPS65910

Hello Everyone,

I posted this question in power management forum without any replies, so trying it again here.

We have recently switched our main processing core to use AM3359 and are in the process of developing our first board with the AM335x Starter Kit as reference.

We definetely need our board to start up, the moment power is applied, without having the user to press a button.

I have searched the forums and net to find a solution to achieve this with TPS65910A3 and have not yet found a method that works.

I tried soldering an R and C as described below (taken from a forum post :http://e2e.ti.com/support/power_management/pmu/f/43/t/191121.aspx)

R = 510K (0402)

C = 10uF (0805)

Tested on AM335x Development Kit (i replaced R112 to 510K, and soldered C=10uF between pins 2,4 of SW5),

I am able to start the starter kit the moment power is applied, but restarting it happens only after a pause of approximately 30 seconds. I guess this is because of the capacitance. Trying lower capacitance value doesnt provide enough delay to start the board.

Instead of using a digital circuit that simulates the button press here to PWRON pin, is there any configuration for TPS65910A3 that achieves this ?

I will be thankful for any suggestions / solutions.

Thanks very much in advance.

Ram

  • 0
    TI__Guru**** 393215 points
    Hi Ram,
     
    One way is to have the PWRHOLD signal tied to the input voltage. Keep in mind though, that the maximum input voltage for PWRHOLD is +5.5V, so you may need to add a divider.
  • 0 in reply to Biser Gatchev-XID
    Intellectual 705 points

    Hi Biser,

    You are awesome. Thanks a lot. It works.

    For others who want a detailed answer: I modified the starter kit as follows to start without pressing the power button:

    remove R27 that connects PWRHOLD to VAUX33.

    connect PMIC pin 1 (PWRHOLD) to VBAT.

    The board starts now as soon as DCIN is applied.

    Ram

  • 0 in reply to shriram
    Prodigy 10 points

    This solution work like a charm with the original SD delivered with the EV kit, but did not work at all with the latest SDK (7.0.0) sd card image (pre-compiled one).


    There is an error with I2C bus, (cannot read eeprom on boot time), so the card cannot boot. as the TPS65910 is connected to I2C, I suspect something wrong with this.

    I end up with a 100uF in // with 10k resistor soldered in parallel of power switch, it do the tricks.