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TPS76901-HT: parrallel LDO??

Tracy Wotherspoon54
Prodigy 240 points
Part Number: TPS76901-HT
Other Parts Discussed in Thread: TPS7H1201-HT

Hi all,

I’m not sure if this post should be here or in the power management group. However my application runs at 200 Deg C and is very space constrained.

I am looking for a small linear regulator to provide 1.8V from 5V @ a max output current of 160mA. I would like to use the TSP76901 but the datasheet spec the max output current at 100mA. A Power boost transistor would probably occupy too much space so my question is would I be safe in putting two of these LDO’s in parallel with say 1 Ohm balancing resistors?  

Everything else in the HT range looks too large eg the TPS7H1201 has a 5.1mmx3.4mm die

rgds

Trace W

  • 0
    TI__Expert 7445 points
    Hi Tracy,

    One can parallel any LDO to get higher output current, and this is true for TPS76901-HT. However when one parallels two LDO, percentage of output current provided by each LDO will depend upon the reference voltage of each. Thus LDO with lower vref will have its loop satisfied first and will provide the load, whereas one with slightly higher vref will provide the balance of load. Thus Vref, layout trace drop etc will all play into it.

    I would think TPS7H1201-HT would be al alternate option if you can live with the package and it will provide better thermal performance as well due to its improved thermal performance.
  • 0 in reply to Ramesh Khanna
    TI__Expert 7445 points

    Hi Tracy,

     see attached sketch highlighting current sharing when paralleling two LDO's.

  • 0 in reply to Ramesh Khanna
    Prodigy 240 points
    thanks for the reply. I agree the TPS7H1201 would be better option but the size of the die and all the passives are the issue. I don't see a sketch?
  • 0 in reply to Tracy Wotherspoon54
    TI__Expert 7445 points

    current share.docxHi Tracy,

    As TPS76901-HT does not have any special feature designed to ensure current sharing.  thus

    Reference variation

    Layout of two LDO how far they are from each other / drop in the circuit

    If we have two LDOs with slightly different voltage the which ever LDO has the lower output voltage will supply most of the current and rest will be provided by 2nd LDO.

    see attached sketch -  Let me see if it uploads properly.

  • 0 in reply to Ramesh Khanna
    Prodigy 240 points
    yes the sketch uploads fine and I understand what you are saying.

    I was goining to add a 1 Ohm (or smaller) series resistor in the output of each LDO commoned to a capacitor. The idea is to minimise the difference in output current as use to be done with a parrallel bipolar transistors .

    The LDO's are adjustable the question arises should the feedback potential divider be pre or post the series networks? If post would one feedback network surfice?
  • 0 in reply to Tracy Wotherspoon54
    TI__Expert 7445 points
    Hi Tracy,

    I have send you an email thus you can email me a sketch highlighting as to how you are attempting to ensure that the two LDO's will current share.