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Customizing Power States

Justin Forrester
Expert 1015 points
Other Parts Discussed in Thread: AM3517, TPS65023

I am in the process of configuring the AM3517 SOM-M2 to run in a very low power sleep mode.  So far the lowest I have been able to go is 20mA. My goal is to achieve a 1mA or lower sleep current draw.  The supplier, LogicPD, has confirmed that this is possible, but it may require building the power state from the ground up.  However, I have been unable to find information on configuring the power states in the TI processors wiki.  Where would be a good place to start in adjusting the power states?  What Kernel files would need to be modified?  I would greatly appreciate any instructions you can provide, resources you can link me to, or other general suggestions towards achieving my goal.

Background: My pad configuration is minimal: 5V to MAIN_BATT_IN, ground lines, UARTs 1-3, and ethernet. VDDSHV is at 3.3V. Current is measured globally from my variable voltage supply, with all external ICs removed and ethernet disconnected. I am using the Linux PSP to configure the Kernel and u-boot.  The Kernel is configured with power management and debugging, with USB, graphics, multimedia, and sound disabled.  The only u-boot modification is the ETK lines have been muxed to GPIO.

  • 0
    TI__Expert 4590 points

    I just checked the product brief of AM3517 SOM-M2 from LogicPD at:

    http://www.logicpd.com/sites/default/files/1014275C_AM3517_SOM-M2_Brief.pdf

    It suggests that SOM board has Ethernet, WLAN and Bluetooth populated. Not sure if you have already done so, but before getting to deep sleep mode, you could turn off the power to these devices from TPS65023.

  • 0 in reply to Sanjeev Premi
    Expert 1015 points

    There are two SOM versions, one with WLAN/Bluetooth and one without.  Both have Ethernet populated. Right now I am working with the one with Ethernet only, although in the near future I will likely start working with the wireless SOM as well.

    How do I go about turning devices off using the TPS65023? Looking at the datasheet, it appears that you can write to its registers using i2c. However, when I attempt to access it (using i2cdump and i2cget) I get the following error: "Error: Could not set address to 0x48: Device or resource busy"

    Thanks,

    Justin

  • 0 in reply to Justin Forrester
    TI__Genius 16690 points

    Unfortunately, the lowest power consumption in standby mode for AM3517 is 12 mW in 1.8 V VDDSHV and 15.5 mW in 3.3 V VDDSHV. Therefore, it's not possible to meet the 1 mA sleep power at the battery input. I would suggest you to consider OMAP35x or AM37x if the 1 mA standby power is critical to your project.

  • 0 in reply to kshin
    Expert 1015 points

    Kazunobu,

    Since HECC is also a requirement, we need to stick with the AM3517 at this point.  4.7mA at 3.3V (15.5mW) will have to do for now.  As such, I would still like assistance obtaining the minimum possible current draw.  Thank you very much for giving me a precise number.  I am definitely disappointed that LogicPD gave us incorrect information.

    Is the suggestion above, with adjusting the state of the TPS65023, a good route to explore?  If so, I still need a response about accessing it.  Any advice regarding power would be appreciated.

    Thank you!

    Justin

  • 0 in reply to Justin Forrester
    TI__Genius 16690 points

    Hello Justin,

    AM3517 supports only one power domain, so the power supplies from TPS65023 shouldn't be turned off during suspend/resume for AM3517. I have replied my suggestions to your another post before. Did you have a chance to try it ?

  • 0 in reply to kshin
    Expert 1015 points

    Unfortunately the suggestion in the other thread did not help.  Perhaps I should take a different route.  Rather than adjusting my current setup, if I were starting from scratch with the SOM, what would I need to do to achieve the minimum of 4.7mA stated above?

  • 0 in reply to Justin Forrester
    Intellectual 310 points

    I'm not sure if this is still an active project, but Logic PD released their new Wattson software for the AM3517 EVM today which will help you see actual power consumption across all power rails on the CPU and SOM design.  There is an adapter required to connect to the PC available from this website: http://createnewstuff.webs.com/breakoutboardwattson.htm

    The Logic PD software is available from here: http://www.logicpd.com/wattson

    -A