Stupid Maxim powerpump chips!

[robbert]

Geez.. just fried my third 3 bucks chip! Damn!

So I made a powerpump. 9V DC in, 18V out. That works. Added a BS250P transistor on the positive line to protect against wrong polarity. Worked fine.

Dunno how I fried the first one, but the second one dies by using the wrong polarities at the ouput jack. Woops.
The third just died by taking the jack out of the socket. Doh!

What I can do to prevent this? So I am safe at the input, but how to protect the output? :cry:

[toneman]

I believe the *max* input on the MAX & the 7660 is 9VDC.
that's the absolute max.   Recheck the datasheet.
Maybe U R exceeding maxV when U unplug(?)
The 340xx & 78/79xx regs' appnotes suggest a "kickback" diode,
2 prevent output discharge thru the internal pass tranny.
Look at the datasheets.
Since there is no *real* 9VDC reg, U probably use a 5VDCreg and
bring it up to 9VDC(?)  Try adjusting reg down a little, say to
8.5VDC.  It wont hurt the pedal sound, but it just may save your
MAXchip......also, add the diode 2 the input DCreg.
stayprotected
tone

[robbert]

Minimum input voltage is 1.5, max. 10.5
I use a regular Boss adapter, so it's around 9.4, so below maximum.

Kickbackdiode... sounds good, will look into that!

[niftydog]

it could be a similar problem that you occasionally get with LM317 regulators. They tend not to like having their output voltage higher than their input voltage. And, usually one has a cap on the output which holds the voltage when you disconnect the power to the input... thus potentially damaging the device. This is the phenomenon refered to by toneman that can be fixed with a diode or two.

Check out the datasheets for LM317 and other regulators.

double check the datasheet for any recommended protection circuitry... like this;

Code Select Expand

Ensure that VOUT (pin 5) does not go more positive
than GND (pin 3). Adding a diode in parallel with
C2, with the anode connected to VOUT and cathode
to LV, will prevent this condition.

so it's around 9.4, so below maximum.

max is 10V... have you actually checked that 9.4V with a multimeter? "regular boss adapters" often exceed 9.4 volts (the unregulated ones, that is!).

[robbert]

Thanks, thanks.. learning something new here every minute


I'm sure it's 9.4 Volts. Maybe few more or less, I have a pretty cheap DMM

I've used two 10uF/50V caps, and two 1N5817 diodes to increase Voltage. What diode's would you suggest to put parallel as mentioned, could I used the 1n5817 for this purpose too?

[niftydog]

probably ok, but if it were me I'd use something more generic and hardy like a 1N4002 or 4003. The 5817 is rated to 20V, the 4002 is 100V! Just to be on the safe side... but hey, use what you've got!

[robbert]

Thanks! Will try tomorrow, still have two spare 1044's left