BF706 Power consumption

Hi,

We have developed a hardware consisting of BF706 as the main controller. I am facing power issues with this. It is drawing more current. I am using only the SPORT of BG706 which is configured to operate with external clock and in TDMA mode. The external clock is 1MHz. Our application is running successfully on this h/w, but its drawing more current.

My observations:

  1. When the hardware is powered on (No code present in the flash. BF706 configured to boot from external flash) with regulated DC input of 7.5 V, the current drawn by the h/w is around 30mA.
  2. When I connect my JTAG emulator to this hardware, the current increased to around 100mA. Is it OK??
  3. When I run my code in emulator mode with out any traffic at the SPORT, the current drawn is around 120 mA.
  4. In the above condition with traffic, current drawn is around 140mA.

My querries:

  • Why is the current drawn in emulator more is more...??
  • I need to reduce the current drawn by the h/w. What options do I have...?
  • In actual application, the SPORT traffic is always present, so I cant use the processor sleep mode or hybernate mode.
  • All the peripherals except for the SPORT are disabled. Then why my h/w is drawing more current. Is there any thing to be done with the un-used pins from h/w point of view...?

Thanks and Regards,

  • Hello,

    I suspect that the increased power you see is caused by the emulator setting clock frequencies when it connects according the values in the following file:

    C:\Analog Devices\CrossCore Embedded Studio 2.1.0\System\ArchDef\ADSP-BF706-resets.xml

    You can fix this by modifying the clocks settings in the file or by explicitly setting the CGU in your application. I recommend doing both to avoid confusion. If you followed the termination instructions in the data sheet Designer Quick Reference you should not have any floating inputs causing additional power consumption.

    Regards,

    Joe

  • Thanks Joe,

    This answers my query related to point no.2.

    Yes, I am modifying the clocks in my application. The CCLK is around 350MHz, and SCLK is around 180 MHz. The SPORT External clock is 1 MHz. As I said, this SPORT is always receiving data and that need to be processed always. Hence cannot use deep sleep or Hybernate  modes.

    We have followed the guidelines mentioned in the data sheets to deal with the unused pins.

    Can you suggest any solution to reduce power consumption from coding point of view?? i.e. any guidelines or coding techniques that could help in reducing the power consumption?

    Thanks & Regards,

    Srikanth.