Powering by 1*AA battery - Page 1
Forum section: electronics / projects

author: 001
author_rank: Super Contributor
timestamp: December 13, 2018, 07:17:57 pm
content: Hi!I see lot of calculators use single AA/AAA batteryWhat the right way to boost 1.2V to 3.3-5V for MCs?Can You post some standard circuit (built-in NiMH charger will be ok too)?Thanx

author: ogden
author_rank: Super Contributor
timestamp: December 13, 2018, 07:26:38 pm
content: Check datasheet of TI TPS6126x. Also ON Semiconductor offers pretty popular boost converter IC's for single alkaline/nimh cell.

author: Dave
author_rank: Super Contributor
timestamp: December 13, 2018, 07:32:33 pm
content: Calculators use ASICs (the black blob in the middle of the PCB) that are designed to use the wide-ish voltage span of the single alkaline battery directly.I know this isn't a solution to you, just wanted to share a tidbit that you might find interesting.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: December 13, 2018, 07:42:36 pm
content: MCP1640 Single Quadruple-A Battery Boost ... - MicrochipGoogled gives a nice reference design with low IqA couple of years old but I like it.

author: james_s
author_rank: Super Contributor
timestamp: December 13, 2018, 07:46:45 pm
content: There's an open source project called the Backwoods Logger that runs months on a single AA or AAA battery. Have a look at that for an example of a boost converter. I don't remember what IC it uses but I built the AAA version years ago and it runs a very long time.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 13, 2018, 08:06:03 pm
content: Quote from: NivagSwerdna on December 13, 2018, 07:42:36 pmBeware the Iq specs on these ICs - it is usually sourced from the boosted output, so draw from the battery will be multiplied by the step-up ratio. Not usually an issue for cylindrical cells though.

author: mariush
author_rank: Super Contributor
timestamp: December 13, 2018, 08:13:58 pm
content: Go to any distributor of electronic components and select switching regulators, then filter results to show BOOST or (step-up) regulators, and then further filter to show only the ones that can operate with MINIMUM VOLTAGE below your single battery voltage, for example 1v or less.From there, you choose a regulator based on how much current your product will use - for example if your microcontroller project won't ever consume more than 50mA, then you could choose a regulator that's designed to output maximum 100-150mA.Here's a starting point:https://www.digikey.com/short/j1105qHowever, you'd still have to check the datasheet and see graphs and charts, because for example you'll find such regulators that can start and function with low voltage, but the output voltage will depend on the input voltage level - below 1v, the chip may only output up to 3.3v, and from 1v and higher, the chip may output 5vHere's an example: MCP1640 from Microchip :https://www.digikey.com/product-detail/en/microchip-technology/MCP1640T-I-CHY/MCP1640T-I-CHYCT-ND/2258621On 1st look, it's a chip that can work from 0.8v and can output up to 350mA... but, check the datasheet :http://ww1.microchip.com/downloads/en/DeviceDoc/20002234D.pdfYou can see on the first page that it says : Up to 96% Typical Efficiency and Iout > 100mA @ 1.2v Vin , 3.3v Vout ... but there's no 1.2v Vin and 5v Vout so you can scroll down and on page 5, you'll find Figure 2-6 , 5.0v Vout Efficiency vs Iout and there, you can see that the black solid line that represents 1.2v cuts at 100mA ... so with just 1.2v input, the chip can't output more than 100mA at 5v. You can also see that it's not quite 96% efficient at such big voltage difference, with just 1.2v it's the most efficient at around 30mA output, and at that point it's around 82% efficient.You have example circuits on the 2nd page in that datasheet, and you can read the datasheet to understand more about how the chip works.

author: DaJMasta
author_rank: Super Contributor
timestamp: December 13, 2018, 08:38:25 pm
content: As mentioned, the micro used also can have a built in boost converter, and there are a number of general purpose micros for low power use that have an integrated low power boost converter, but the broadest range of options is going to be in dedicated boost converter ICs. You will typically need a handful of passives and maybe a diode other than the IC itself, but you can select something optimized for your expected current draw for best efficiency.

author: Nauris
author_rank: Regular Contributor
timestamp: December 14, 2018, 04:06:55 pm
content: There are also microcontrollers that work straight from AA battery voltages, for example Lapis ML610 series work down to 1.1 V.

author: wraper
author_rank: Unknown
timestamp: December 14, 2018, 04:40:43 pm
content: You can simply use MCU that can be powered from a single cell directlyhttps://www.silabs.com/Marcom%20Documents/Resources/C8051F9xx-media-presentation.pdf

author: Kasper
author_rank: Frequent Contributor
timestamp: December 14, 2018, 04:43:04 pm
content: +1 for Mariush.Never trust the specs on the first page of the datasheet. A boost regulator will probably not deliver its max current when fed with its min voltage.If you find a regulator that can boost from 1V to 3V and output >200mA, let me know.

author: ogden
author_rank: Super Contributor
timestamp: December 14, 2018, 04:44:36 pm
content: Quote from: Nauris on December 14, 2018, 04:06:55 pmRight. There'sMSP430L092going down to 0.9V (w/o booster) as well. AFAIK this is one chip out of whole msp430 family with such voltage specs.