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Discrete Voltage Supervisor using TLV3691

Samuel Jaffe
Mastermind 25590 points
Other Parts Discussed in Thread: LM8365, TLV3691, LMP7300, REF1112, TPS3839

Hi E2E,

I'm trying to make an ultra-low-power voltage supervisor with discrete parts (comparator, voltage ref...) for a customer.

I'm coming from this E2E post which looked at single-IC solutions.  In short, I need a voltage supervisor with:

  • Ultra-low power (<1uA)
  • ~100mV hysteresis
  • Negative-going threshold voltage somewhere within 2.3V to 3.08V.

The TPS3839L30 (and family) fits all specs except for hysteresis (in the 20s of mV)

The LM8365 (and all other parts) don't fit the power budget.

I've read through How To Implement Voltage Monitoring and it states that the lowest power option would be the parts shown above, but another option would use discrete parts (comparator, voltage reference...).  The TLV3691 has an Iq of 150nA, but the lowest current voltage reference I found pulls around 3uA.

In your experience, is there any way we can hit these specs?

Thanks,

-Sam

  • 0
    TI__Mastermind 49906 points

    Hi Samuel,

    Sounds like the LMP7300 is what you want...but it is much higher current that you would like.

    The REF1112 shunt reference can be run down to 900nA. I have used it <1uA, but the temp range will be very limited.

    Keep in mind that the external resistor dividers will burn most of the current - unless you want to deal with >100M resistors. A 10M resistor is 100nA per volt. The hysteresis feedback network will be interesting... :^)

    Nanopower designs are not easy...And you may have difficulty obtaining unpopular resistor values above 22MEG, so try stick to "common" 5% values.

    You can probably squeeze 2-3uA out of the REF1112 and the TLV3691 and some very high value resistors. That will get you the best flexibility.

    Regards,

  • 0 in reply to Paul Grohe
    TI__Mastermind 25590 points

    Paul,

    Yeah, looks like it'll be well above our power requirements. We'll circle back around to the TPS3839 and see if we can't get it to work for the application.

    Thanks for this great information!

    -Sam