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OMAP-L138: calarification for CVDD=1.3v use case in power estimation spread sheet

Naoki Kawada
Guru 19890 points
Part Number: OMAP-L138
Other Parts Discussed in Thread: OMAPL138

Hi, 

My customer is considering using OMAP-L138 with 1.3V core voltage and now they are considering the power consumption in their use case.

The power estimation tool is available here :

Their understand they still have to use 1.2V (nominal) for the following lane.

  • SATA_VDD
  • PLL0_VDDA
  • PLL1_VDDA
  • USB_CVDD

Now there questions are:

1) When we saw the spread sheet, at least SATA_VDD and USB_CVDD values are changed based on the specified CVDD value. For example,we saw 10.7mW for CVDD=1.3v with the use case of Typical 456Mhz and USB2.0 enabled. However, we saw 9.1mW for CVDD=1.2v. This implies the power consumption for these lane is changed based on actual CVDD. They think this is not correct and the fixed 1.2V should be used for these calculation even if we are in CVDD=1.3v use case. Can you comment on this ? Should they still rely on the value calculated by CVDD=1.3v ?

2) The are assuming the power lane for USB0/1_VDDA33 and DVDD3318_A/B/C is separated each other in their use case. The spread sheet, however, don`t care about this scenario and just sums up the power consumption as *IO33*. When they estimate the value only for USB0/1_VDDA33, can they just use the value on USB2.0 column for the estimation ? For example, we saw 41.4mW in case of Typical 456Mhz ,USB2.0 enabled, and HS Transition enabled in the spread sheet. Is this value applicable to USB0/1_VDDA33 power consumption ?

Best Regards,
NK

 

  • 0
    TI__Guru**** 161600 points

    Hi,

    1). Use the value calculated by CVDD = 1.3V. The power estimation spreadsheet provides estimates of the upper bounds in an application-specific loading and peripheral utilization scenario. The spreadsheet data may be considered maximum average power consumption; the actual observed power may vary.

    2). They can simulate for all USBs, in my opinion values should be similar (when input parameters are similar).

    As a note you can take into account the statement in the wiki:
    Testing in the real world
    If you are doing power design analysis, you should be aware Logic PD provides Wattson software for the OMAPL138 EVM which will help you see actual power consumption across all power rails on the CPU and SOM design. The software visually shows you which power rails are onsuming the power and when they are switching on and off in your application. There is an adapter required to connect to the PC available from this website: createnewstuff.webs.com/breakoutboardwattson.htm The Logic PD software is available from here: http://www.logicpd.com/wattson


    Best Regards,
    Yordan