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LM3424: Limiting current/Current capability of Vs pin in LM3424??? Not mentioned in the datasheet..

Akash Dey
Prodigy 30 points
Part Number: LM3424

The maximum current budget I can draw from the Vs reference pin isn't given in the datasheet. This is not mentioned in the datasheet. From my present context I want to load this pin with about 4-5 mA of load. I actually want to put an analog comparator which will be fed V(TREF) & V(TSENSE) at the inverting & non-inverting terminals respectively. The comparator swing will be powered up by Vs(2.45 V) & GND. The output will be fed to an LED in series with a resistor. So, I want to light up an LED when the system starts dimming due to thermal foldback.

Please reply as soon as possible.

For other such pin i.e. Vcc it is 20-25mA clearly stated in the datasheet.

  • 0
    TI__Mastermind 28655 points

    Hello,

    The datasheet shows a test case at 1 mA for Vs.  It was really intended to be a reference voltage for circuitry that could run from Vcc or elsewhere.  You could use Vcc to drive the comparator which would give enough voltage room to drive an LED with an appropriate resistor in series.

    Vs may be capable of higher current but it is not characterized beyond 1 mA and the reference voltage could be off if loaded beyond 1 mA.  It is generated from Vcc.

    Thanks,

  • 0 in reply to Irwin Nederbragt
    Prodigy 30 points
    OK. So, it means 1mA is the limiting current for Vs. Drawing more current will lead to limiting action which will cause the 2.45 V reference voltage to drop.
    Can you please give some idea of the load regulation at this pin. I mean is it good if I'm drawing 500-750 uA without significantly loading the Vs pin?
  • 0 in reply to Irwin Nederbragt
    Prodigy 30 points
    OK. So, it means 1mA is the limiting current for Vs. Drawing more current will lead to limiting action which will cause the 2.45 V reference voltage to drop.
    Can you please give some idea of the load regulation at this pin. I mean is it good if I'm drawing 500-750 uA without significantly loading the Vs pin?
  • 0 in reply to Akash Dey
    TI__Mastermind 28655 points

    Hello,

    It's not the limiting current, it is the range the IC is tested to to hold the tolerance in the datasheet, 2.45 - 2.5 - 2.55 volts.  If more current is pulled from the pin it may cause regulation issues and go out of this range.

    Thanks,