Here is an app note from Microchip that describes how to built a single battery boost converter. It provides a way to power higher voltage circuits with a lower voltage battery.
The design is based around the MCP1640 IC. It is a 350mA 500Khz boost converter with an integrated switch. Due to it’s design the device requires very few external components to function. One Inductor, two capacitors, and two resistors are all that is needed.
The efficiency ranges from 60% to 90% depending on the load and input voltage. Check out the graph below.
Perfect timing. I was just thinking about how to do this. I have a need to get 3.3 from a single NiMh AAA (low current application).
The MAX1796 & MAX1797 produce 3.3 V without the resistor divider, will start up with 0.85 V and keep delivering 3.3 V as your battery runs down to 0.7 V, and can reach 95% efficiency. Just connect the FB pin to the OUT pin for 3.3 V operation. Fewer parts; better performance.
@rsdio,
The MAX1796/1797 are around $10.00 USD each in unit quantity (Digi-Key has stock). The Microchip MCP1640 is $0.44 USD each or 96% less in unit quantity (Digi-Key again). This is typically the case. Maxim parts are outrageously priced and often very difficult to source. No, I’m not going to grovel for a sample from Maxim.
The Eval Board for the MCP1640 is P/N MCP1640EV-SBC. It is $19.99 in unit quantity. The eval board has two boost converters in slightly different configurations.
Touché, Drone.
I frequently complain that Linear Technology chips are way more expensive than Maxim. I’m looking at $5 for the MAX1797, but I did not realize the Microchip part was so cheap (although I do not see it available for US$0.44 until quantity 100). I believe that the Maxim part handles 67% more current.
Thanks for the tip. I’ll search Microchip for regulators next time I need a boost.
Whoops, you’re right. The unit-quantity MCP1640 price from Digi-Key is $0.60 USD ea. for the 8-DFN package and $0.70 ea. for the SOT-23-6. But that’s still a looong way from $10.00 for the Maxim part.
You said, “I frequently complain that Linear Technology chips are way more expensive than Maxim.”
Huh? We’re comparing Maxim and Microchip here. I agree, Linear can get pricey sometimes. But Maxim and ADI take the cake IMHO in the “outrageously priced and hard to find” parts contest.