Hi, I am trying to make it so that the 1.8_en line is pulled up by resistor to 1.8v and passes trough a transistor to then drive a mosfet. I got the part where i pull high the line before the transistor right, but when the transistor is off, i need the line on the mosfet side to be tied to ground since i cant leave it floating. But with that setup, when i turn on the transistor, there is a voltage divider effect which i dont want. How can i go about doing that? the pull up is because there is an active low component that turns on under a voltage treshold but over that treshold it is simply floating so i pull it high.
Strange construction.
Better tell us what you want to achieve by posting the whole project.
Leo..
basically i have a TPS3839G33DBZR that checks wether the battery voltage is at 3v, if it goes under that, it triggers reset which i want to make it turn off the mosfet, thus cutting power to the whole system. the switch conected to the base of the transistor is simply a power switch, if it is on it lets the high logic turn on the mosfet, if it is low, it doesnt and the mosfet is turned off, once again cutting power to the whole system. its basically a UVLO with a power switch.
if you want i can share the whole power management circuit but you got most of the relevant parts in the picture previously linked
So you want the power switch only to work (turn on the fet) if the battery is >3volt.
Correct?
well yeah, if the power switch turns on and the reset is pulled low, its not going to change the state of the mosfet, i was wondering if i could use something similar to this instead TPS259521DSGR
Try this. No transistor.
Connect the reset output of the supervisor directlty to the gate.
Use a 10k resistor between battery switch and gate. Add a 100k resistor between gate and source (ground), to stop the gate from floating.
Leo..
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you're right, i didnt think of the voltage the actual switch could bring! no need to have a pullup with that! So this would be correct?
Yes.
The switch powers the gate through the 10k resistor.
The supervisor can override that by pullling the gate low.
All that's left is to draw diagams according conventions.
Power on top, ground down, signals left to right.
Leo..
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Alright, thanks a lot for your help!