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chathurayasasvi , 01-30-2026, 04:42 AM

Hi everyone,

I’m working on a power management circuit for an Orange Pi 5 Pro project and could use some eyes on my logic.

The Goal:

I need a "Smart Load Switch" circuit between my 5V PoE supply and the SBC that meets these requirements:

Auto-Power On: When PoE is plugged in, the device must turn on automatically after a short delay.

On-Command Switch-Off: The Orange Pi must be able to signal the circuit (via GPIO or I2C) to cut its own power (software shutdown).

Reliability: I previously tried a discrete P - N chanel Mosfets solution but ran into issues where the trigger signal couldn't properly pull down the N chanel gate to cut power. I was thinking about to add a Optocoupler but again more components to the BOM. Then,

I’ve changed to using the TPS22998 load switch (schematic attached). I’m also evaluating several control methods to manage the timing and the "Always On" 3.3V rail.

I’ve attached several iterations I'm considering:

Option A (RV-3028-C7): Using an RTC's interrupt/event output to trigger the load switch.

Option B (74LVC1G123): Using a monostable multivibrator for the timing delay.

Option C (AM1805): A more robust RTC/Power management IC approach.

The Switch: My latest draft uses the TPS22998RYZR.

Questions for the Community:

TPS22998 Implementation: For those who have used this chip, what is the best way to ensure it defaults to "ON" at plug-in while still allowing a GPIO from the Pi to pull the ON pin low for a shutdown?

The "Auto-On" Logic: In the block diagram, I’m looking for the simplest way to drive the Load Switch after a certain time. Is the RTC-based interrupt the most reliable way to handle this, or is there a simpler passive circuit I'm overlooking? Or maybe a chip ? ( Must be not expensive)

Pull-up/Pull-down Conflict: I want to avoid the "ghost powering" or partial-on states I had with my discrete FETs. Any specific advice on the ON pin strapping for this specific SBC?
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QDrives , 01-30-2026, 08:32 PM

Since you have the 'always on' 3.3V, why not a simple MCU?

Robert Feranec , 02-02-2026, 04:28 PM

did you consider some chips? I used some before ... this is just an example I quickly found, but there are many with different features: LTC2955 https://www.analog.com/media/en/technical-documentation/data-sheets/2955fa.pdf

chathurayasasvi , 02-08-2026, 08:43 AM

Yeahh but because of another firmware overheard, that's not an option but thank you for commenting for this post.

chathurayasasvi , 02-08-2026, 08:50 AM

@Robert Feranec Yes I went though this and it is kinda expensive but honestly thank you for commenting for this post. I tested Ambiq AM1805AQ with P chanel mosfet. I was able to control it , the way i want. At the moment I am doing a repetitive test. I had a little problem where mosfte is not turning off completely. Then I realised the signal comes from Ambiq is 3.3V and my main voltage line is 5V because of that Vgs become -1.7V which makes P chanel is partially on. Then I added a 74LVC1G17 buffer. Now everything is working, So far so good.