mbt28
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Maximum Power Output From DSI port

Mon May 28, 2018 10:20 am

Hi,

What is the maximum current that I get from 3.3V output of display connector? If I feed 3.3V trough GPIO can I get more more current from this connector?

Thanks

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mahjongg
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Re: Maximum Power Output From DSI port

Mon May 28, 2018 12:38 pm

NO!

The 3V3 comes from exactly the same 5V to 3V3 converter source as the 3V3 going to GPIO's, the amount the converter can deliver depends on the model pf PI you are using, but even in the best case it will not be much more than a few hundred mA, probably much less.

Don't feed 3V3 to the GPIO from an external 3V3 source, or you will damage the PI (the converter).

the DSI ports power lines are dimensioned ONLY for the power requirement of the camera logic NOTHING ELSE!

especially it was never intended to power a LED Ring, as some Chinese re-sellers sell.

Using such a ring might damage your PI and camera!

mbt28
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Re: Maximum Power Output From DSI port

Mon May 28, 2018 1:06 pm

mahjongg wrote:
Mon May 28, 2018 12:38 pm
NO!

The 3V3 comes from exactly the same 5V to 3V3 converter source as the 3V3 going to GPIO's, the amount the converter can deliver depends on the model pf PI you are using, but even in the best case it will not be much more than a few hundred mA, probably much less.

Don't feed 3V3 to the GPIO from an external 3V3 source, or you will damage the PI (the converter).

the DSI ports power lines are dimensioned ONLY for the power requirement of the camera logic NOTHING ELSE!

especially it was never intended to power a LED Ring, as some Chinese re-sellers sell.

Using such a ring might damage your PI and camera!
Thank you very much for your reply. This changes everything now.

What if I only power an attiny40 chip? Or the best is avoiding this 3.3V power source completely coming from pi?

I am using rpi 3 b+.

Thanks

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rpdom
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Re: Maximum Power Output From DSI port

Mon May 28, 2018 4:33 pm

mahjongg wrote:
Mon May 28, 2018 12:38 pm
the DSI ports power lines are dimensioned ONLY for the power requirement of the camera logic NOTHING ELSE!
Display, not Camera. Camera would be CSI port. The same power capabilities still apply though.

hippy
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Re: Maximum Power Output From DSI port

Mon May 28, 2018 5:04 pm

mbt28 wrote:
Mon May 28, 2018 1:06 pm
What if I only power an attiny40 chip? Or the best is avoiding this 3.3V power source completely coming from pi?

I am using rpi 3 b+.
If you are drawing only a few milliamps you would possibly be okay but you would never know for sure unless you can find a spec for the connector and cable, and after having tried it.

The reduced Pi 3B+ schematics show DSI and CSI 3V3 pins connected to the 3V3 pins on the GPIO connector and powered from VOUT1 of the PMIC chip. It therefore shouldn't matter where you extract 3V3 from, apart from PCB track, connector and cable ratings.

The PMIC chip appears capable of supplying 3V3 at 1A5 though whether it can or not on a Pi is unknown to me. That 3V3 goes to other parts of the boards, and I would expect to the SoC and other components not shown on the reduced circuit, so it is difficult to say how much current can be drawn from 3V3 on a Pi.

We don't know how much the PMIC can actually supply, we don't know how much the board uses, and that will vary depending on use, so we don't know what capacity is spare, and that will be reduced if cameras, displays and other things are connected. The amount one can draw from any 3V3 pin is not officially stated anywhere.

The best way to provide 3V3 for external circuitry would be to take a feed from your 5V power in to the Pi and separately regulate that to 3V3 oneself.

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