circuit protection schematic design (OrCAD)

[Skyland]

I have designed a protection circuit for my pcb and I would appreciate having some feedback before starting the PCB design.

The circuit is broken down as follow;

-ESD protection provided by a one channel IC

-low pass filter to suppress noise above 4.5Khz

-pmos to protect against reverse polarity

-crowbar for overvoltage protection

-current sensor which is connected to a uC ( ideally I would like the op amp to work with the PSU IN in the range 3.3v to 16v)

The maximum voltage is 16V and the minimum votlage is 3.3V.


Edit:

The current monitored is in the range of 0 - 1A . ADC is from 0 - 3.3V

The actual models used have been implemented in the schematic for clarity.

The supply voltage range is from 3.3V to 16V

The low pass filter has been replaced by a ferrite bead

Differential Op amp is used for current monitoring with 165K for R load to provide the adequate gain (0 to 3.3V input to the ADC).

[Rerouter]

As a suggestion to your schematic keep your grounds on the bottom line, the funky resistor tied to ground tied to negative of battery is not that easy to read at a glance,

other than that, i would probably recommend a resistance in front of the op amps sense line, the crowbar circuit will take some time to fire and during that time it would better protect the esd diodes on the input if you had something to limit the current flowing through them,

[free_electron]

First of all : what the hell is up with those damn dots everywhere ?

Second. This protection circuit doesnt protect at all. I can fry this without problems.

That thermal fuse should be the first thing i hit, followed by the transient suppressor.
The coil cannot have a capacitor before it. If i inject a spike the cap before the coil would recirculate the energy. The path before the coil needs to be open. So actually you need to hit the coil first, then the fuse then the transient suppressor.

The crowbar ? That is too slow for any kind of surge. For long duration events that will work but you will burn off a lot of power...

As for current monitoring , by a cpu ... By the time that thing reacts your circuit is fried....

[mij59]

Hi,

Why did you chose a high voltage mosfet with a rdson of 30 Ohm and a threshold voltage of -2 to -4 V ?
At 3.3V the mosfet will probably not turn on.
I may be confused by the dots, but R5 is connected parallel to the 3.3V supply.