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TPS709: Dropout Voltage at Low Current

John Turner, Valhalla
Prodigy 75 points
Part Number: TPS709
Other Parts Discussed in Thread: TPS7A24, TPS715A-NM, TLV701, TLV704

Hi,

I'm hoping to use the 1.8 Volt version of TPS709 is a "phantom" powered application with an output load current of less then 5uA. The challenge is that the input voltage varies from 4.8 Volts down to 2.5 Volts which is below the operating specification. Basically I'm wondering if there is any latitude in the drop out voltage because of the low current draw? 

If the TPS709 isn't the best choice could you recommend and alternative. Ideally, I'm looking for a 1.8 Volt, 1 mA regulator that operates between 2 and 16 Volts with an operating current of less then 10uA.

JT

  • 0
    TI__Mastermind 29170 points

    Hi John,

    The TPS709 should work in your application with plenty of margin.  You were probably looking at the dropout voltage at full load, but at lesser values of load current this dropout voltage requirement is reduced.  See this plot in the datasheet. At 5uA of current and 700mV of headroom you should be fine.

    Thanks,

    Stephen

  • 0
    Prodigy 75 points

    Hi Stephen,

    Thanks for the response. I think asking about dropout voltage might have be misleading. The part is specified for minimum operation at 2.7 Volts or the Output voltage plus 1 Volt whichever is greater. The part does seem to regulate down to 2.5 Volts but below that the output drops (or turns off).

    I guess a better way to ask the question, is will the part operate with an input of 2.5 Volts with an output current of 5uA? As well, what is the under voltage lock out voltage for the part?

    JT

  • +1 in reply to John Turner, Valhalla
    TI__Mastermind 29170 points

    Hi John,

    I see the question now.  The part does require 2.7V to have all of the internal circuitry operating as anticipated.  There is no formal UVLO circuit, which is the reason for the 2.7V minimum.  It is probably incorrect to say that it will not be functioning in some capacity at 2.5V, as you can see in figure 6-34 in the datasheet.  However it is not specified at 2.5V.  You could purchase an EVM to test the TPS709 at your operating conditions, or you could try a different LDO.

    Would the TPS7A24 work for you?  It goes down to 2.4V minimum but has slightly higher operating current at 1mA at 15uA.

    Other devices which may work:

    TPS715A-NM
    TLV701
    TLV704
    TLV715

    Thanks,

    Stephen