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SmartReflex Power Supply Design - Proper Design Parameters?

Trevor Fox
Intellectual 340 points
Other Parts Discussed in Thread: LM21212-2, LM10011

Hello,

I am designing power supplies for the DSP C66xx Keystone 1 Devices.


I am planning on using the LM21212-2 power regulator for the DSP Smart reflex.

Since the Power voltage going to the DSP CVDD can be adjusted by the LM10011 to any value between .7 to 1.1V, this presents an unavoidable design quandary - which voltage should one optimize their power supply for? I can't see any 'Smartreflex' option for the Ti power supply simulator - I have to select one voltage, one frequency, one set of compensation resistor/capacitors. Is there any recommended tact to use for this power supply design?

  • 0
    TI__Guru**** 161600 points
    Hi Trevor,

    I've forwarded this to the hw experts. Their feedback will be posted directly here.

    Best Regards,
    Yordan
  • 0
    TI__Mastermind 42545 points

    Hi Trevor,

    We can't give you a specific voltage since each C66x part can request a different voltage depending on the SmartReflex value needed. We can narrow the range a bit. While SmartReflex allows for a voltage range from 0.7V to 1.1V, the C66x parts will only use the portion of that range from 0.85V to 1.1V with a majority of the parts asking for a voltage closer to the higher value. Note that the power supply circuit must provide a stable voltage for the entire range which could be requested by the part.

    Regards,

    Bill

  • 0 in reply to Bill Taboada
    Intellectual 340 points

    Hi Bill,

    thank you for the reply and information.

    I understand that the voltage can vary from .85V to 1.1V device-to-device.

    It sounds like what you are saying is that the power supply should be simulated at .85V and 1.1V and this should cover all use cases.

    I was just hoping that since it's a TI DSP and a TI power supply, there was some single [ideal] value that could be simulated but it doesn't sound like that's the case.

    I appreciate your response.

  • 0 in reply to Trevor Fox
    TI__Mastermind 46460 points

    Trevor,

    As you realized, you should simulate at both extremes to validate that your power supply design constraints are met.  Since the designs normally have significant margin and stability, this will not be a problem.  You will also need to analyze supply performance at both low and high current conditions.  You should complete the Power Consumption Estimation spreadsheet to determine maximum power consumption.  Then you should use a value of about 30% of this maximum for the lower load limit.  This range will cover all of the load current amounts due to variations in supply voltage, temperature and silicon process variation.

    Tom