10 volt to 9 volt

[Marcvv]

I have a regulated multiple isolated power supply that gives 10 volt on each outlet. In principle that is fine for most of my pedals.
I am using a voltage doubler in one of my pedals build around a MAX1044. I would like to bring down the 10 volt to 9 volt to be sure not to blow the MAX1044.
Can I use a 9 volt regulator (I have a UA7809) for that or will that drop the 10 volt too low??

Thanks, Marc

[CynicalMan]

The dropout voltage is 2V, so it probably would drop it lower than you want. A 9.1V zener regulator maybe?

[JKowalski]

A silicon diode in series will drop it down 0.6-0.7 volts.

[Marcvv]

Hi,

Thanks for reacting. I will try that.

Can I use any silicon diode (1n4148 or 1n914 is what I have at hand) to put in series?

Marc

[Scruffie]

Just to mention, Frequency Central reported that the MAX1044 in his Murder One Design ran fine at 12V for many hours and seeing as they're rated for 10V anyway... Might be safe enough on its own.

[earthtonesaudio]

In my opinion, the best solution for taking exactly 9V from 10V is a low dropout (LDO) regulator.

[Marcvv]

Well I have been using that MAX1044 without problems for a long time on 10 volt but it is not working anymore so that is why I was thinking about bringing the voltage down once I use a new one



Alex:

Low drop out regulator: I am not familiar with that. Can you explain that to me please?

Thanks, Marc

[earthtonesaudio]

A low dropout regulator will keep regulating even when the input voltage becomes very close to the desired output voltage, allowing a low "drop" between input and output.  A standard linear regulator typically needs at least 2V difference between input and output to keep regulating.

more info

[Marcvv]

A low dropout regulator will keep regulating even when the input voltage becomes very close to the desired output voltage, allowing a low "drop" between input and output.  A standard linear regulator typically needs at least 2V difference between input and output to keep regulating.

more info

Thanks for explaining. I could have used that search function myself

But... do you have any experience with a specific Low drop regulator that you would recommend for this.

[merlinb]

A power diode like a 1N4001 would drop closer to 1V, and would be ideal.

[earthtonesaudio]

A power diode like a 1N4001 would drop closer to 1V, and would be ideal.

The 1044 can only supply 20mA and at that current a 1n4001's forward voltage drop is closer to 0.6V.

After reading the datasheet more closely I think using a LDO is a bit excessive.  Maxim guarantees the part to 10V, so it should be fine with that.  Adding a single series diode as many people have suggested would allow your power supply to fluctuate by +6% without damaging the MAX1044.  That's probably sufficient protection.

[trjones1]

You could replace the max1044 with a tc1044 which is rated up to 12V.

[JKowalski]

Well, the only reason for this is to drop the voltage so it isn't skirting the edge of the 1044's maximum ratings, so it's not like you need a perfect 9 volts.

[cpm]

are you doubling voltage with the MAX? if so, how much current your circuit does need?

i used a 4049 inverter ic as voltage pump. Seems like a convenient setup since they are cheaper than MAX and LTC chips, and can be powered up to 15v

[frequencycentral]

NE555 doubling is even cheaper: http://www.diystompboxes.com/smfforum/index.php?topic=80007.0

[Ronsonic]

Hi,

Thanks for reacting. I will try that.

Can I use any silicon diode (1n4148 or 1n914 is what I have at hand) to put in series?

Marc

Measure the drop using a diode tester in you DMM if you've got. Otherwise I would use two of those in series to get the drop you need. It will be very close to a 1V drop.

[Marcvv]

Hi all,

Thanks for reacting.

- I will try the silicon diode I have in series and measure the drop and if necessary I will add another. Good tip.

- Yes I could replace the 1044 with a 1054 but this is what I have at hand. Thanks for that tip anyway.


Marc