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I'm attempting to interface a TPS61235P boost converter to an Arduino Pro Mini (3.3V Vcc), and while I can get it to turn on, I can't for the life of me get it to turn back off.

I currently have a 1M resistor pulling it down, and a 10k resistor to an output on the Arduino.

Before driving the pin high, the converter is (correctly) disabled. When I make the pin go high, it turns on just fine. But when I turn the pin low, figuring it'd pull it to ground combined with the 1M resistor, the converter stays on. On top of that, my code indicates the OUTPUT pin state is high as well, despite me setting it low (I have an OLED display on the Arduino).

The enable pin stays at 5.15V constant, despite originally only supplying it with 3.3V. Its almost like it feeds itself, because not even the Arduino can drive it low, I must ground it with a wire and then it stays low, even after disconnecting the jumper wire.

If I disconnect the enable pin from the Arduino, the output pin switches as it should to low. It reads high again the moment I plug it back onto the enable pin of the converter.

Even with jumpering resistors to the enable pin, the only way I can get this thing to turn off is to jumper it to ground with a wire, no resistors.

What's going wrong?

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ You have to guarantee that the pin is below 0.4V to get it to turn off. Measure the voltage on the pin when the output is low. If it's >0.4V then figure out why and address that problem. \$\endgroup\$ – John D Feb 9 '17 at 0:20
  • \$\begingroup\$ Thats the problem I'm having. I just checked and it stays at 5.15v constant, despite originally only supplying it with 3.3v. Its almost like it feeds itself, because not even the Arduino can drive it low, I must ground it with a wire and then it stays low, even after disconnecting the jumper wire. \$\endgroup\$ – Jeff Feb 9 '17 at 0:48
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    \$\begingroup\$ (a) I know you have tried to describe the circuit in words, but it would help readers to give you answers, if you provide a detailed & accurate schematic diagram of your design. A photo of a hand-drawn diagram would be a start, if that's all you've got, or use the schematic editor built into the text editor (click the electronic components symbol). (b) The physical layout of the components is also important with SMPS like that boost converter. Therefore please also supply a photo of your boost converter inc. all its related components (i/p & o/p capacitors, inductor, pull-down resistor etc.). \$\endgroup\$ – SamGibson Feb 9 '17 at 1:24
  • \$\begingroup\$ Thank you, I didn't even realize that existed! \$\endgroup\$ – Jeff Feb 9 '17 at 1:38
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It sounds like you have a connection between the boost converter's Vout pin and the Enable pin. If so, the converter's output is driving its own Enable pin high. This is collaborated by the comment you attached to your question. Perhaps your pullup resistor is in the wrong place?

In any case, the Arduino output pin may get damaged by the overvoltage condition. It sounds like it's still working (so far), but something to keep in mind.

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  • \$\begingroup\$ This was it. Its so simple and I completely missed it. It really makes sense as that package was hard as all hell to solder. Thank you! \$\endgroup\$ – Jeff Feb 9 '17 at 1:40
  • \$\begingroup\$ @Jeff No problem! Glad to help. \$\endgroup\$ – bitsmack Feb 9 '17 at 6:55
  • \$\begingroup\$ @Jeff Oh, wow, I hadn't noticed the package. Not many people can say that they've soldered a 2.5 mm VQFN :) \$\endgroup\$ – bitsmack Feb 9 '17 at 6:56

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