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LP3996: Internal reference, bypass resistor, and POR pin capabilities

Part Number: LP3996

A few questions regarding the LP3996 dual regulator:

1. What is the internal reference voltage?  Seems like it must be < 1.0V.

2. What is the value and (probably sloppy) tolerance of the internal resistor biasing the Cbypass pin?

3. What is the current sinking capability of the POR pin?

Thanks, Best, S. Dunbar, Field Applications, Colorado

  • Hi Dunbar,

    1)  I believe the reference voltage is 0.8V, as that is the lowest output voltage. I am ordering an EVM to confirm.

    2) We are looking into this. 

    3) The rated IOL is 250uA to hold VPOR low

    Very respectfully,

    David

  • Thanks, I missed the 0.8V option.

    I see in the data sheet that POR has a spec'ed VOL of 20 mV typical, when sinking I,SINK = 250 uA. This would imply about 80 Ohms for the pull down MOSFET. Based on this I would think the actual rating of the pin would be higher?

    Thanks again.
  • Hi,

    It may be, but that spec gives a worst case scenario to design a system with and ensure that it is at a valid logic low. If you need more sinking capability do realize the Vol voltage will go higher, and you need to ensure that your it's still a valid logic low for your system. For that model the FET as a resistor (as you did with the 80 ohm), and just use ohm's law. Be aware that this is a model for the FET and is only an estimated max.

    -David