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C5515 Sleep Mode Consumption

David Whitehouse
Prodigy 190 points
Other Parts Discussed in Thread: INA219

Hi,

I have a custom C5515 board that I'm trying to get into a minimum power state.  It is currently running at 8MHz from the 32kHz oscillator with PLL enabled with the UART active with the core IDLEing and I've shut down all clocks I'm not using.  The core is powered at 1V05 and all IO is 1V8 - the power being consumed from these rails is 2.3mW (700uA at 3V3 into the switchers) including external 1V8 memory etc.  However I've got another 6mW on the 3V3 rail disappearing somewhere.  The USB part of the chip is powered but it should all be shutdown (I've followed the sequence in the C5515 DSP System User Guide 1.5.3.4.1) - I can't see any specification for the quiescent current for the USB module into USB_VDDOSC, USB_VDDA3P3 and USB_VDDPLL - the System User Guide suggests there might be a reasonable quiescent:

"Stopping clocks to a peripheral only affects active power consumption; it does not affect leakage power consumption. USB leakage power consumption can be reduced to zero by not powering the USB."

but gives no clue to what it might be.  What should I expect as a quiescent when the USB is shut down?

Many thanks,

Dave

  • 0
    TI__Mastermind 23785 points

    Dave,

    It is referring to grounding all the supply pins related to USB when the USB function is not implemented. You can refer to Table 3-21 in data manual, SPRS645B for all the USB related supplies and descriptions.  Also, I want to point out is in section 1.5.3.4 of same document, it explains how to  handle the USB oscillator.

    Regards.

  • 0 in reply to Steve Tsang
    Prodigy 190 points

    Steve,

    Thanks for the reply.  In my application I am using USB, but in the low power sleep mode it can be disabled (only needs UART communications) - in this UART only state I'm looking to shut every off.  I've shut off the oscillator as described... Are datsheet type figures being worked on for the C55X5 peripherial power consumptions, or this the current information as much as we'll be getting?

    Thanks,

    Dave 

  • 0 in reply to David Whitehouse
    TI__Mastermind 23785 points

    Dave,

    You can refer to each individual peripherals User's Guide for current information. A couple of additional info I would like to bring up from other customers applications. Avoid floating inputs. In a CMOS circuitry, a bi-directional pin is floating when the output is tri-stated while the input driver is not driven. A lot of pins are being mux'ed for different peripherals and are bi-directional pins, make sure there are no floating inputs and gounded their individual power pins if possible.

    Regards.

  • 0 in reply to Steve Tsang
    Prodigy 190 points

    Steve,

    I've diabled a few more bits (and the zero offset on the INA219 I was using to measure the current was giving me an additional 1.5mA) and now I'm down below 1mA so I'm happy. 

    Thanks,

    Dave