Problems when using the LTC1440 and LT3009-5

[yh_ang]

I want to design a circuit whose function is to detect the input voltage Vout+,when it is greater than the threshold Vth=8V,The LT3009-5 operates and output 5V. When the input voltage is less than the threshold Vtl=3V, the LT3009-5 is disconnected from the previous circuit.

why V(vu3out) is too small only 100mV in 0.45s?

great wishes
flora,
2018,4,10

 

[ChrisP58]

While you can sometime get away with using the generic nmos and pmos devices in LTspice, they can can often cause problems, as some of their operating parameters may not be what you need them to be.

Do this.
- Right click on the pmos device > Pick new mosfet > AO6407
- Right click on the nmos device > Pick new mosfet > AO6408

See if that makes a difference.

Also, the LT3009 should have a 1uF cap at it's input.

PS. It's helpful to include your .asc file when asking about a simulation. That way someone can quickly run your file to see what's wrong, without having to rebuild it first.

 

[yh_ang]

ChrisP58
Thanks your advice!
It's very helpful to use AO6407 etc. the LT3009 should have a 1uF cap is right.but the main reason of this circuit can't work is the use of LTC1440. LTC1440 has a small differential voltage：VTH-VTL, I must design a new one instead of using LTC1440.

great wishes,
flora.

 

[yh_ang]

here is my simulation.
Vth=5.45V Vtl=4.89V。