XL6009 Switching Converter – Warning

The XL6009 is a nifty, inexpensive switching voltage regulator from XLSemi. (see datasheet). There is also the XL6019 (see datasheet). They are great parts and operate over a wide input voltage range at high efficiency and their internal switch can deliver substantial current. They can operate in boost and SEPIC/Buck-Boost configurations

HOWEVER you need to be cautious when using the ENable pin (2): the datasheet indicates that EN is a TTL compatible input and considers anything over 1v4 as High (Enable) – that’s good. It also mentions that if left unconnected, the pin floats high (enabled) – that’s also fine.

What wasn’t apparent to me, and certainly isn’t spelled out in the datasheet, is that when the EN pin floats high, it is at Vin and can source enough current to do damage. So if you are using the converter to boost say 12V to 24V, you’d better not connect that EN pin directly to a microprocessor GPIO because the processor pin will be at 12V and will be destroyed! (as I learned the hard way)

The solution of course is simple, just use the processor GPIO to drive a transistor in an open drain/open-collector arrangement to disable the converter. A common 2N2222 or 2N3904 should work just fine over the full input range of the XL6009. Live and learn.