3.7V to 9V DC to DC boost step-up converter design help!

Question

I need serious help choosing an IC for my project. I need a step-up boost converter to power my device from a 1000mAh or 2000mAh lithium ion battery. So far I have measured that my device only draws around 25mA when I wired in an ammeter. From looking at the data sheets and using "quiescent" current ratings, I calculated that the device would draw 62.8mA of current. Since I am using an ATmega32, I looked up what the absolute worst maximum current draw would be and found that an absolute max of 400mA could be drawn from the atmega32, but I will likely never really see that.

Based on that, I've been looking for an IC that will boost 3.7V DC to 9V DC with a max output current of around 500mA. Can someone advise me on why I am having a difficult time in finding such an IC and can anyone make any suggestions for a circuit that I can incorporate?

Answer 1

Really? About a minute on DigiKey and I was able to find several hundred ICs which meet your requirements. For example, this chip.

To find more, go to the "PMIC - Voltage Regulators - DC/DC Switching Regulators" section, specify an output current of 500 mA or higher, specify boost and buck-boost topologies, then sort on price. There are lots of options to choose from that meet your voltage requirements.

General procedure when using a switcher:

1. Read the datasheet.
2. Read the datasheet again.
3. Design your circuit based on the typical application circuit provided in the datasheet. Often these will even include specific suggestions for passives - you can use these, or equivalents.
4. If possible, simulate it. Linear Technology and TI are both good for this, as their free SPICE offerings (LTSpice and TINA-TI respectively) include models of most of their switchers.
5. Switchers are pretty sensitive to PCB layout considerations. Most switcher manufacturers include a recommended layout which helps you minimize EMI concerns - using this is highly recommended.

Finally, lots of manufacturers provide software tools which are essentially idiot-proof for DC/DC switching power supply design. National Semicondutor (now TI) WEBENCH is a good example of this. It only recommends TI parts (obviously) but if you punch in your requirements and it will spit out a list of possible designs including a full schematic, BOM, and estimated price for 1000 units. Pretty handy.