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Author Topic: GPIO_1 3.3v current  (Read 3130 times)

cio74

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GPIO_1 3.3v current
« on: November 24, 2014, 10:47:57 PM »
Hello,

I am planning to use the 3.3v on the GPIO_1 header to power an additional board, any safe current value that can source without causing any issues?

Thanks.

JohnS

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Re: GPIO_1 3.3v current
« Reply #1 on: November 24, 2014, 11:04:26 PM »
Which board?

Datasheets will tell you.  Use schematic....

John

cio74

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Re: GPIO_1 3.3v current
« Reply #2 on: November 24, 2014, 11:35:45 PM »
Lime A10

I couldn't find where it says.

Gerrit

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Re: GPIO_1 3.3v current
« Reply #3 on: November 24, 2014, 11:36:26 PM »
http://dl.linux-sunxi.org/A10/A10%20Datasheet%20V1.70.pdf

If they mention the current then it is always 20mA

cio74

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Re: GPIO_1 3.3v current
« Reply #4 on: November 24, 2014, 11:40:09 PM »
I don't believe it's 20mA, it's the same 3.3v routed that they use to power the MCU and the rest. The SMPS chip is rated at 1.2A but the flash, Ethernet PHY and the other will sink some current; the question is, how much is left.

I would expect them do to these computation and to know what the board draws at 3.3v

JohnS

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Re: GPIO_1 3.3v current
« Reply #5 on: November 25, 2014, 12:05:23 AM »
"them" - who?  DIY.  Trivially easy.

John

cio74

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Re: GPIO_1 3.3v current
« Reply #6 on: November 25, 2014, 12:39:37 AM »
Why are you posting in here, you do not help at all, you have replied twice to my post and both are useless.

People like you have negative impact on their business, these boards are not hugely popular and decent people with decent answers is the key to increase interest not the way you reply around.

JohnS

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Re: GPIO_1 3.3v current
« Reply #7 on: November 25, 2014, 02:26:27 AM »
To get you to think.  You've posted one value.  Measure the board (or read data sheets) and subtract.  Allow some leeway.

Sometimes YOU need to put effort in.

John
« Last Edit: November 25, 2014, 02:28:58 AM by JohnS »

dave-at-axon

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Re: GPIO_1 3.3v current
« Reply #8 on: November 25, 2014, 04:30:21 AM »
In a way, JohnS is correct in that you need to find out a lot of this yourself if there is no answer from the forum. These are development boards and as a number of people have seen, they lack a lot of details and things like current draw is one of them. They give an overall consumption. You can probably extrapolate it from the input current. It would be close enough to give you an idea of how much is free for your own use.

How much current do you need to draw from the 3.3V rail? I would guess that up to around 100mA is probably OK. The issue you have is in drawing too much is that the supply rails drop and your board will reset or in some cashes crash from the brown out.

Gerrit

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Re: GPIO_1 3.3v current
« Reply #9 on: November 25, 2014, 02:39:57 PM »
I don't believe it's 20mA, it's the same 3.3v routed that they use to power the MCU and the rest. The SMPS chip is rated at 1.2A but the flash, Ethernet PHY and the other will sink some current; the question is, how much is left.

I would expect them do to these computation and to know what the board draws at 3.3v

Sorry i understood wrong, i believed you wanted to use a GPIO port to feed an other board.
But i also think that the power consumption depend on how busy the SOC is, so its not a static number