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AsianVy , 08-21-2025, 07:57 PM

Hi everyone I'm designing a battery-powered PCB (7.4V, 2S Li-ion) with a user-controlled power switch implementation.

The design uses a TPS22811 load switch to control main power distribution, activated by a small slide switch which also controls the enable pin of the 3v3 buck to power on the load switch. Will this implemenation work?

QDrives , 08-22-2025, 11:09 PM

No.
1) You have 3.3V as the input for the 3.3V.
2) "Not enable" of the 7.4V buck is connected to the "enable"
3) 7.4V from 7.4V?
4) A ferrite bead and ceramic capacitor will cause a resonance. Often at SMPS frequencies
5) Better drawing: have the 'line' of a SMPS from SW output to inductor in the same line. The bootstrap capacitor goes up.

AsianVy , 08-23-2025, 09:43 PM

For the 3V3 I was thinking I had to step it down from the original battery because the output current is too high compared to the slide switch contact current rating

AsianVy , 08-23-2025, 09:44 PM

Would that be the right approach

AsianVy , 08-24-2025, 01:47 AM

and also the 7.4V is to the load switch which goes to other buck converters im not trying to step down a 7.4V to 7.4V just to clarify

Mini , 08-24-2025, 01:17 PM

Nothing makes sense here. There is nothing taking current on enable pin. You can put one resistor in series just in case. It would limit the current. But there is really nothing taking the current on enable pin.

Mini , 08-24-2025, 01:18 PM

You are using 3.3V just for this?

Mini , 08-24-2025, 01:18 PM

I hope your MCU is using 3.3V too?

Mini , 08-24-2025, 01:20 PM

Don't understand anything.

Robert Feranec , 08-25-2025, 11:29 AM

I only had a look at the switch, and the enable pin. Normally I would orient the switch the way, that the common pin is connected to the enable input and the two pins are switching between high and low. But, be very careful, you need to specify the voltage level on the enable pin when the slider is in the middle between the pins, so you will need for example a weak pull down or pull up on the enable pin ... but this depends on what is else is connected to the enable pin as I see EN port there going somwhere else. Hope this makes sense

AsianVy , 08-25-2025, 04:50 PM

I also want the switch to control other buck converters because if I just wire the enable pins to the Vin, when i plug in the battery to the connectors, I fear that the system will always turn on making the slide switch useless

Mini , 08-26-2025, 09:35 PM

If you really want to get help then start by making yourself clear what you want. For enable if it is active high you put pull down resistor like 100k. So your power supply will stay off. If you want to turn on with switch you simply connect it to voltage source.

Robert Feranec , 08-27-2025, 11:39 PM

you can do connect all enable pins together, just be sure they can be controlled by the same voltage level (sometimes there can be maximum level e.g. 5V, sometimes the minimum voltage level that means High can be different) and they work the same way (eg low disabled, high enabled)

Note: often power supplies are switched on in series and often from the highest voltage to the smallest one ... so the output or ideally the power good signal of a regulator with higher voltage will control the enable signal of regulator with lower voltage