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TLV70018 Ground Current

uMin
Intellectual 860 points
Other Parts Discussed in Thread: TLV704, TLV700

Hi,

I have a few questions regards to LDO ground current:

  1. Is Iq (quiescent current) defined as ground current at zero load current condition ?
  2. Is LDO input current = output current + ground current ?
  3. The following graphs are taken from TLV700 and TLV704 datasheet repectively.  TLV700 ground current seems to be proportionally increased with the load current, whereas the TLV704 ground current is relatively constant through out the load current range.  Is there a mistake in the TLV700 graph ? or should the x-axis be input current rather than ground current ?

Thanks,

CM.

 

  • 0
    TI__Intellectual 1260 points

    Hi, CM,

    Please see answers below to your questions.

    1. Yes.

    2. Yes.

    3.  The datasheet is correct. For LDO device, usually ground current will increase with load current increase, but how much it increases really depends on design topology.

    Let us know if this answers your question.

    Thanks,

     

    Su

  • 0 in reply to Su Zhang
    Intellectual 860 points

    Hi Su,

    Thanks for your reply.

    My impression is that in general, the efficiency of a LDO is Vout/Vin, if you ignore the small ground current (or current drawn by the LDO internal circuit).  Looking at the TLV700 graph, it seems to indicate that a 20mA increase in output current also results in an increase in 20mA in ground current.  Is this true ?

    Thanks,

    CM.

  • 0 in reply to uMin
    TI__Intellectual 1260 points

    Hi, CM,

    Actually the ground current for TLV700 is in uA range, so it is about 20uA ground current increase with 20mA load increase.

    Usually for higher load application, the ground current is not a very critical spec. That is why in general the effiviency of an LDO is usually increased by lower quecient current. With higher load application, if the ground current is a very critical spec, then different desgin topology will be used.

    Thanks,

    Su

  • 0 in reply to Su Zhang
    Intellectual 860 points

    Hi Su,

     

    Thanks for your reply.

    Sorry, I did not read the scale carefully at first.  It makes sense now that the ground current increases only in uA range.

     

    Thanks,

    CM.