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Delta Icc Spec?

Paul Joseph
Expert 2785 points
Other Parts Discussed in Thread: SN74LVC14A

 I don’t understand what the DELTA Icc spec is? for instance on the SN74LVC14A, page 6 of the datasheet?

Please explain how this is tested…it does not make sense…what is this DELTA Icc?...is it just a TRANSIENT INCREASE IN Icc?...and if so, why should Icc change if one input voltage is reduced by 0.6V with respect to Vcc?...that would still be a LOGIC HIGH input voltage.

Please advise and thank you.,

 

 

  • 0
    TI__Genius 9085 points

    ΔICC Supply-Current Change

    The increase in supply current for each input that is at one of the specified TTL voltage

    levels, rather than 0 V or VCC.

     

     

    The application note 'Understanding Standard Logic Datasheets' http://focus.ti.com/lit/an/szza036b/szza036b.pdf explains this in more detail on page 52. Though it's only 0.6V less than VCC (and still a logic high) there is increased current flow.

     

  • 0 in reply to Hattie
    Prodigy 70 points

    Page 52 seems to say that the increase is "n x Icc"

    I'm using a SN74LVC1G06MDCKREP, which has an Icc of 10 uA

    Single input

    Would this suggest an additional 10 uA of current, for a total of 20 uA ???

    The SN74LVC1G06MDCKREP datasheet says 500 uA ????

    What if you are at a different voltage differential than 0.6 V, does it increase/decrease ??? over temp ???

    500 uA seems like an awful lot

  • 0 in reply to Hattie
    Expert 2785 points

    So…now my followup question is what is DELTA Icc for an input voltage of +0.6V (i.e. 0.6V greater than the 0V level)…i.e. an imperfect but very realistic logic “LOW”.

     s this question addressed anywhere?...if not, are you confident that I can use the same DELTA Icc spec as for the “0.6V below Vcc” example?

     This is CRITICAL to my designs, because I have an operating mode called SLEEP MODE…and the static Icc of the logic devices is a critical part of this SLEEP MODE CURRENT CONSUMPTION.

    Please advise, thanks!

  • 0 in reply to Paul Joseph
    TI__Mastermind 46480 points

    Hi Paul

      see page 52 for Delta Icc definition. http://focus.ti.com/lit/an/szza036b/szza036b.pdf   I agree it is kind of a silly spec but it is not something we made up. It is a tested and guarranteed level.

    For CMOS parts the farther you get away from the rails the more current you will draw.  The Delta Icc spec is the max current you will see if you stay below .6V or above Vcc-.6V.

    You can draw a lot of current if the input floats around the trheshold region. Here is another appnote that covers floating inputs. http://focus.ti.com/lit/an/scba004c/scba004c.pdf

  • 0 in reply to Chris Cockrill
    Prodigy 70 points

    I need to ask the qustion again. The App Note seems to imply 20 uA, whil the spec says 500 uA

    Can you please talk to that discrepancy ???

  • 0 in reply to J Deigan
    TI__Mastermind 46480 points

    I am not sure wher 20ua comes from but here is the actual data for the LVC1G06. see attached. The spec is per input. It looks like the spec is guardband about 10X but it is still not 20ua.

    ICCT.doc
  • 0 in reply to Chris Cockrill
    Prodigy 70 points

    the confusion is that the App Note referenced above says "that the increase is "n x Icc"", where n (I believe, is 1 input) and Icc (from your datasheet) = 10 uA, giving you an additional 10 uA (so, 10 uA + 10 uA = 20 uA)

    the actual data sheet    _says_     500 uA

    20 /= 500

    we have abandoned this part

    thank you

  • 0 in reply to J Deigan
    TI__Mastermind 46480 points

    That is not the case. It is per input and that includes all Icc. Delta Icc is total Icc current. It is measured at the Vcc pin. you would not add anything else to it. 

  • 0 in reply to Chris Cockrill
    Prodigy 70 points

    what is the Icc of a SN74LVC1G06MDCKREP when its sole input is driven wih Vcc-.6V ???

  • 0 in reply to J Deigan
    TI__Mastermind 46480 points

    I dont have that information. I suspect they went to only testing the top side because it was worst case.

  • 0 in reply to Chris Cockrill
    Intellectual 400 points

    We plan on using the SN74LVCH244ADGVR.

    According to the datasheet the Icc is 10uA, but the Delta Icc is 500uA. According to the app note

    "If n inputs are at voltages other than 0 V or VCC, the increase in supply current will be n × ICC'

    Given that the device is a 2 x 4-bit device, does this imply that Icc would be 8 x 10uA? 

    Can you please clarify? This 10uA seems off because I'm used to seeing Icc numbers in the mA range. Thank you

  • 0 in reply to Anthony Campos
    TI__Mastermind 46480 points

    Icc is tested with all pins HIgh or Low so if the inputs are at the rails the total current will be 10ua  .  Delta Icc is tested single pin so if your inputs are not at the rails you will need to add the current per number of pins to get total Icc.

  • 0 in reply to Chris Cockrill
    Intellectual 400 points

    So for each pin that is HIGH, the Icc increases by 500uA?  So then how is it possible with 8 inputs high or low that Icc is 10uA?

  • 0 in reply to Anthony Campos
    TI__Mastermind 46480 points

    Delta Icc is what would happen if you used a TTL part to drive a CMOS part.  Your input levels would not be at the rails so in this type of situation it would not have Icc if 10ua.

    If you are driving the part with a CMOS part and the input levels are at Vcc or 0V the you would have Icc of 10ua. Icc is measured with the inputs at Vcc or 0V.

    Here is an appnote that explains how each limit is tested and what they mean.

    http://www.ti.com/litv/pdf/szza036b