5V to 24V Step-up Advice

[migsantiago]

Hello!

I want to convert a 5V USB supply to a 24V @ 30mA supply. I will use it for audio signals so I would like it to have a switching frequency of 100kHz or more.

Is there any simple IC that can step-up this voltage with low noise? The 24V load is just 15mA or so, but I am giving it a little extra window of 30mA just to be on the safe side.

Thanks for your tips!!

[tecman]

There are quite a few chips that can do this.  Personally I like the 34063A for doing a variety of SMPS jobs.  It has an internal switch transistor, reference, and error amp.  As far as the noise issue, it will be more a function of the layout, grounding, proper caps and perhaps some additional L on the output as a filter.

Paul

[Zero999]

Does it need to be regulated?

If not you could use a charge pump which needs no inductor, just capacitors and if you make the frequency high, the capacitors can be small ceramic disc.

[migsantiago]

Hi guys!

Tecman, that's a great IC, I checked its formula and you just have to calculate R1 and R2 in order to obtain the Vout you want. I think I will use it just in case nobody else posts a better one. 

http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=mc34063a&fileType=pdf

Hero999, it has to be regulated because it will feed a microphone and the bias voltage may oscillate if the 24V supply is not regulated. 

[NiHaoMike]

There are plenty of boost converter chips out there. Look through the selection menus of Maxim, TI, or Linear, just to name a few.

[migsantiago]

There are plenty of boost converter chips out there. Look through the selection menus of Maxim, TI, or Linear, just to name a few.

Hi Nihaomike!

I was looking for them yesterday in TI.com but I could only find 2. I'd better use one that has been tested and approved by someone else.