I have a circuit that runs 5V. I need to integrate a CO2 sensor that requires 6V. What would be the simplest, most cost effective way to do this? I need about 200ma for the sensor
boardbite's TPS61040 is just one of many step-up converters which will do the job. But it costs 1.88 dollar in 1s at Digikey, while the cheapest I found is only 70 cent. That's the Semtech SC4503.
This is the typical application schematic from the datasheet. Again, this will be similar for many other step-up switchers. The SC4503's reference voltage is typically 1.25 V, so for 6 V out you have to set R1 to 190 kΩ. At 12 V out and 200 mA the SC4503 will have a 90 % efficiency, for 6 V you can expect a slightly higher value. It can supply more than 1 A of output current, so you'll have lots of headroom. Comes in a SOT23-5 package, and the 1.3 MHz switching frequency means you only need a small inductor.
The TPS61040 (from TI), among other adjustable-output step-up regulators, can accommodate 200 mA or more current draw at output voltage of 6V, from input voltage of 5V.
It is available in SOT23-5 package as well as 6-SON (similar to QFN), so you can start with a larger prototyping-friendly footprint, then move on to a smaller one for a final product.
Also, it's a fairly popular and inexpensive part, so you should have no trouble obtaining it. I think it costs a $1-2 in single-unit quantities.
I have used it before (for an LCD backlight application), and had good results with little layout effort (minimal number of peripheral parts, including a 10uH inductor).
Here is its datasheet.
If you can't get that one, frankly there are dozens of options out there; just look under stepup/boost regulators in Digikey or Mouser. I just find that particular one to be convenient and reliable.