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latching push-button controlled MOSFET switch with IRF7319

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luca0074:
Hello all

I have integrated the "soft power switch" from Sparkfun (https://cdn.sparkfun.com/assets/5/6/6/6/0/SparkFun_Soft_Power_Switch.pdf) in my handheld device.
Due to the unavailability of the SIL2308, I used the IRF7319TRPBF as in the original design (http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/raspberry-pi/on-off-power-controller).

Here is the schematic of my implementation:


I have the following problem:
I can only switch on the device via S1 (or ON_BUTTON_EXT) if I have vBus > 4.4V.

Is this due to the IRF7319TRPBF used (https://www.mouser.ch/datasheet/2/196/Infineon_IRF7319_DataSheet_v01_01_EN-1228230.pdf) or is there another cause of the problem?

Is there an easy fix for the problem?

Thanks for your help!

Greetings Luca

eblc1388:
No. The problem is not due to the IRF7319TRPBF.

Try, in the following order:

1. increase value of C3 between R14 and R15 from 0.1uF to 1uF, then retest, if still fails, then keeping C3 at 1uF, do
2. increase value of C5 from 10uF to 22uF.

luca0074:

--- Quote from: eblc1388 on September 10, 2021, 03:44:17 pm ---No. The problem is not due to the IRF7319TRPBF.

Try, in the following order:

1. increase value of C3 between R14 and R15 from 0.1uF to 1uF, then retest, if still fails, then keeping C3 at 1uF, do
2. increase value of C5 from 10uF to 22uF.

--- End quote ---
Hi eblc, thanks for your suggestions!
1. didn't work.
2. this just made the time longer that is needed for shutdown the device.

Peabody:
The threshold voltage of the SIL2308 has a minimum of 0.5V and a maximum of 1V.  But the IRF part has a minimum of 1.0V, with no maximum shown.  So maybe that difference is enough  to make it not operate properly at low voltages.

Would the processor power up fast enough that it could turn on the N-channel and keep the power on with just a brief button press?  If so, you could move all the latching stuff into the processor and greatly simply the circuit.

eblc1388:
This type of circuits behave heavily on the nature of the connected load. Most hated load with large capacitor connected.

Can you also confirm the circuit does not work even if no output load is connected? This might point to a different approach in modifying the component values.

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