IOIO-OTG VReg dead?

[Lagz Moncs]

Hello,

I suspect my IOIO-OTG voltage regulator is gone. The power led will not light up anymore when IOIO is supplied through VIN. IOIO is not detected when plugged to Android device and I cannot get outputs. Is my hunch right?

I can still get the power light to light up though when connecting IOIO-OTG via USB to a host Android and I can still control the status led.

Is there a way to 5V power the IOIO through microB terminal so then I can still use it as host to Android device or might not be possible at all?

[Ytai Ben-Tsvi]

It is indeed fried.
You might be able to bypass the regulator by supplying 5v directly to the 5v rail. Make sure nothing gets hot when you do that. If it does, you may need to desolder the switcher.

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[Lagz Moncs]

Okay I will try that, thanks.

[Gustav Sohtell]

Hi!

The same thing has happened to me to two of my IOIOs. They still work when connected to my mac but neither 5V nor 3.3V rail has any voltage when power is connected to VIN.

I have two questions:

Can I fix them by adding external 5 and 3.3V regulators so that they will still work in host mode? (and check for heat)
I tried adding 5V and then connecting to an android tablet but that did not seem to work.

Does anyone have any guesses of how I might have broken them? In both cases I'm guessing that I was connecting/disconnecting a USB cable to an Android tablet. Could I have had a grounding error or something?

Best regards,
Gustav

[Ytai Ben-Tsvi]

Yes, you can bypass the 5V VREG with an external one. Before you do that, make sure there is no short between 5V and ground caused by the fried VREG. If there is, desolder the switcher. Make sure your external supply can source at least 1A. Your 3.3V VREG is probably OK.

To my knowledge, the possible ways to fry the switchers are reverse voltage or over-voltage (even very short spikes). The latter may be caused by using Vin > 10V over long wires (high inductance).

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[Gustav Sohtell]

Thank you! I'll try that.

I have about two meters of 24V wire from power source, but I have a 7812 regulator on the circuit board with the IOIO. Perhaps I should add some capacitors to even out small ripples or even a 15V zener diode over the VIN.

Thanks!

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[Ytai Ben-Tsvi]

A TVS diode is probably a better choice. Zeners cannot handle a lot of current. The problem with TVS is that they have a big voltage gap between when they're fully off to fully on. Am LDO is not a good idea if you have any non trivial load connected to the 5V rail (such as an Android trying to charge itself). It will get extremely hot. Interestingly, when LDOs fail they tend to short the input to the output...