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I am designing a breakout PCB for a microcontroller which operates at 3.3v and I'd like to add a jumper which specifies if whether the 3.3v signal from multiple GPIO pins will first go through a bi-directional 3.3v <-> 5v IC (when the jumper pins are connected) or not, in order to increase versatility. This functionality will be implemented on 16 GPIO pins.

Also, I prefer each breakout board pin to output the same current as the MCU(20mA typical / 50mA max.) in both 3.3v and 5v modes, when the respective GPIO is set to output via software.

Is there any way to implement this? If yes, then how, and which parts should be used?

Thanks in advance.

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    \$\begingroup\$ There really aren't any ways to implement this which don't have one consequence or another, so to come up with a useful approach you must consider the specific requirement. \$\endgroup\$ – Chris Stratton Nov 18 '20 at 20:52
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A 'level shifter' IC, which you realize you need, would have two 'power pins'... Call them "VCCA" and "VCCB". So if you were shifting 3V-5V, you'd set VCCA=3V, and VCCB=5V.

To adjust what the 2nd voltage is, i.e. you want to change VCCB, you can easily do that with a 1P2T switch. The switch would have 3V & 5V feeding it, and the 'common' pin connects either 3 or 5 to VCCB power pin on the shifter IC.

Pretty simple really....

You'd probably not want to flip the switch when the device is powered. You didn't say whether or not you wanted to do that.

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  • \$\begingroup\$ Thank you for the response. I was not sure that this kind of ICs behave correctly when VCCA = VCCB. More specifically, which IC should I use to get started? Also, the switch won't be flipped when the device is powered. \$\endgroup\$ – Kozma Nov 18 '20 at 21:43
  • \$\begingroup\$ We use this one: ti.com/lit/ds/symlink/… Datasheet doesn't say VCCA can't equal VCCB, only that VCCB can't be LOWER. (which is a non-issue for you I think). \$\endgroup\$ – Kyle B Nov 18 '20 at 21:49
  • \$\begingroup\$ Thank you very much, have a great day! \$\endgroup\$ – Kozma Nov 18 '20 at 22:03
  • \$\begingroup\$ These parts aren't magical devices free of consequences... \$\endgroup\$ – Chris Stratton Nov 18 '20 at 22:58

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