IO PWM voltage on 6HC
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I'd like to put a large PWM fan for my electronic case, and I found one from Noctua. But the specs says 12V (which is fine if I put the jumper on the 12V rail) but 5V PWM control voltage. (5.25V absolute maximum rating). What is the IO voltage on IO 4-6 ?
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@kuon 3.3V. What is the model of fan ?
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Sure about that? There is a mosfet with a flyback didode on those outputs
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@bearer There are mosfets on heaters and fan outputs, but not on IO ports. Unless... @kuon has OUT4-6 in mind wich are actually fan outputs, and I belive are open drain type on PWM pin, so they do not apply voltage by their own on that pin.
@kuon If You just want to use ordinary PC Noctua fan on 4 pin fan header OUT4-6 it will work.
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Noctua fans have pull-up on the PWM within the fan, however they do work with a high level of 3.3V (up to 5.25V). Since they have a pull-up in the fan, what the actual voltage will be is a bit unclear - Noctua don't specify the strength of their pullup.
Is the OP discussing IO_4 to IO_6 or OUT_4 to OUT_6? The post says IO, but reference to jumper on 12V rail implies OUT.
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Yes, I did mean OUT_4->6, I mixed it up. Noctua has this spec for PWM: https://noctua.at/media/wysiwyg/Noctua_PWM_specifications_white_paper.pdf
But yeah, if PWM pins are open drain it should work.
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Yes they are open drain, and when I test them I use Noctua fans.
