tonesenna 20 Posted October 18, 2012 Share Posted October 18, 2012 Hi everyone. I've been working on a battery powered boosterpack, hence the "RocketFuel" name. The features are pretty standard: Li-Ion charger: BQ2057 LDO regulator: TPS78233 (150mA Iq=500nA VDO=130mV) Current shunt monitor: INA219 Before starting prototyping this board I have a couple doubts for which I'd like to have some feedback: 1- Is is usefull to have the possibility of mounting a Lithium primary cell (Eg: Lithium Thyonil Chloride - 3.6V) for "standby" applications that require extremely low idle currents and also low battery self-discharge? The PCB allows one to use one such cell in 1/2 AA format, leaving the charger unmounted 2- Is a shunt monitor useful at all? I understand that for most applications current consumption is very bursty and an I2C shunt monitor isn't all that useful. O the other hand, designs using the ARM launchpad or the C2000 might benefit of having a way to monitor supply current, voltage and calculated power. So what do you guys think? 3- What would be a "confortable" format for a Li-Ion / Li-Po battery? Would an RCR123A be suited or are there better alternatives? I found it extremely difficult to find a small sized Li-Ion battery with a standard form factor. The closest that I got was an RCR123A, which is basicaly a CR123A shaped Li-Ionbattery that includes the protection circuitry. The 18650 and even 14500 are too bulky and don't fit well in the boosterpack format. I'd like to keep the board as small as possible. 4- Are150mA enough for most applications of the LaunchPad? My objective here is to keep Iq to a minimum, for cases where one would decide to use a primary battery. Here's a draft version of the PCB. Once I have these details Ironed out I hope to mount a couple units and try then out. Regards, --to Automate and bluehash 2 Quote Link to post Share on other sites
GeekDoc 226 Posted October 18, 2012 Share Posted October 18, 2012 This seems pretty viable, but I'll leave the technical opinions to those smarter than I on such matters. This might go pretty well with the VFD clock, depending on capacity. Quote Link to post Share on other sites
bluehash 1,581 Posted October 18, 2012 Share Posted October 18, 2012 Can the charging circuit support a higher capacity battery. Idea looks great otherwise. Quote Link to post Share on other sites
Philipp 56 Posted October 18, 2012 Share Posted October 18, 2012 The idea is great, but why do you prefer LiIon over LiPo? Lipo cells are very common and well accessible for anybody, and they are flat with capacitys from 350mAh - 1500mAh in a size suited for use with the launchpad. One can stick them to your booster or to the bottom side of the launchpad. Don't get me wrong, you LiIon approach looks very professional in contrast to a LiPo taped to the bottom side of a PCB, but those LiIon round cells are quite bulky. For use with the MSP430 Launchpad the LDO is very well suited because of the wide voltage range of the MSP430. If the battery voltage goes below 3.3130V the LDO will go into pass through mode and you can use a full battery cycle. Although you're desing incorporates a protected battery, you might want to add some kind of under-voltage sensing, maybe with the MSP430 itself sensing battery voltage and disabling the LDO if it goes below 3.0V. I'm not familiar with the C2000 Launchpad, but I know that the Stellaris Launchpad wants 3.3V, so maybe a boost converter would be better suited to utilize a full battery cycle without VOUT dropping below 3.3V. The processor on the Stellaris Launchpad however is rated for Voltages between 2.97V - 3.63V, so if you want to go really low power your LDO design might be superior to a switching regulator. If you wan't to support the Stellaris Launchpad, you might consider to use the XL booster pinout because it has 5V broken out, hence you could charge the battery while debugging the Stellaris with a single USB cable. more info on the XL booster interface: http://processors.wiki.ti.com/index.php ... _Interface Nice work! EDIT: just stumbled across sparkfun's 'Polymer Litium Ion Batteries'. I'm not sure if they are LiPo, LiIon or sth new, but their physical size is nice: https://www.sparkfun.com/products/339 Quote Link to post Share on other sites
tonesenna 20 Posted October 18, 2012 Author Share Posted October 18, 2012 Can the charging circuit support a higher capacity battery. Idea looks great otherwise. The BQ2057 can handle much larger charge currents, IIRC up to 2A (probably even more because of the external pass device). When running from a USB port however, the current must be limited to 500mA. For higher charge rate we'd need an external power input jack and a wall adapter capable of supplying the additional current. For higher charge currents a switched mode charger might be a better solution. High amperage wall adapters are somewhat rare and probably expensive =) Regards, --to Quote Link to post Share on other sites
GeekDoc 226 Posted October 18, 2012 Share Posted October 18, 2012 just stumbled across sparkfun's 'Polymer Litium Ion Batteries'. I'm not sure if they are LiPo, LiIon or sth new, but their physical size is nice: https://www.sparkfun.com/products/339 From what I understand, LiIon and LiPo are the same technology with different names, differing only in form (rigid, usually round, protective case for LiIon; flat, rectangular, plastic covering for LiPo). Of course, IANAEE. Quote Link to post Share on other sites
tonesenna 20 Posted October 18, 2012 Author Share Posted October 18, 2012 Thanks for your input blue, lots of contributions there! The idea is great, but why do you prefer LiIon over LiPo?Lipo cells are very common and well accessible for anybody, and they are flat with capacitys from 350mAh - 1500mAh in a size suited for use with the launchpad. One can stick them to your booster or to the bottom side of the launchpad. Don't get me wrong, you LiIon approach looks very professional in contrast to a LiPo taped to the bottom side of a PCB, but those LiIon round cells are quite bulky. I totally agree. My first thought was to use a taped battery. I decided otherwise because I wasn't able to find a battery that would fit the boosterpack with a decent capacity (>400mAh) and with high availability. I want to leave the buttons of the LP available so the bottom side of the boosterpack must be trimmed out. Doing rough math (assuming a 40 pin interface), I have an area of 40mm x 55mm beneath the boosterpack where I might stick a battery with double-faced adhesive tape. Do you suggest any website in Europe where I might find this type of batteries? RCR123 is really bulky (availability isn't shiny, either), and that's what's been keeping me back from sending the PCB to build a couple pieces. For use with the MSP430 Launchpad the LDO is very well suited because of the wide voltage range of the MSP430. If the battery voltage goes below 3.3130V the LDO will go into pass through mode and you can use a full battery cycle. Although you're desing incorporates a protected battery, you might want to add some kind of under-voltage sensing, maybe with the MSP430 itself sensing battery voltage and disabling the LDO if it goes below 3.0V. I'm not familiar with the C2000 Launchpad, but I know that the Stellaris Launchpad wants 3.3V, so maybe a boost converter would be better suited to utilize a full battery cycle without VOUT dropping below 3.3V. The processor on the Stellaris Launchpad however is rated for Voltages between 2.97V - 3.63V, so if you want to go really low power your LDO design might be superior to a switching regulator. If you wan't to support the Stellaris Launchpad, you might consider to use the XL booster pinout because it has 5V broken out, hence you could charge the battery while debugging the Stellaris with a single USB cable. more info on the XL booster interface: http://processors.wiki.ti.com/index.php ... _Interface I'll take a look into your suggestion. If I manage to move the battery to the back of the PCB using adhesive tape, the additional PCB area may allow to take some of those aspects into account without compromising low power operation. EDIT: just stumbled across sparkfun's 'Polymer Litium Ion Batteries'. I'm not sure if they are LiPo, LiIon or sth new, but their physical size is nice: https://www.sparkfun.com/products/339 If I extend the board area to cover the top (FET) of the LP, this battery would fit nicely. Is there any site based in europe where I might find simillar devices? Regards, --to Quote Link to post Share on other sites
Philipp 56 Posted October 18, 2012 Share Posted October 18, 2012 leaving the buttons available is recommended by the booster design guide, too. I can only give some links to stores located in germany, but farnell or rs online cover most parts of europe. Berlin based Sparkfun Reseller: http://www.tinkersoup.de/product_info.p ... 1576b2246a Farnell / element14: http://de.farnell.com/bak/lp-523450p-is ... dp/2077888 Pollin.de, cellphone battery, no leads but darn cheap: http://www.pollin.de/shop/dt/MzMwOTI3OT ... BC80S.html Ebay has plenty, but all reasonable priced ones are from hongkong. I'm really surprised how hard they are to source in large quantities, they are definetly not that accessible than I thought. I'm an quite active model pilot and i usually salvage good cells out of bad battery packs, so I#m never short on Lipo's.. tonesenna 1 Quote Link to post Share on other sites
tonesenna 20 Posted October 18, 2012 Author Share Posted October 18, 2012 Thanks blue! Indeed they are difficult to source, specially with appropriate dimensions that would fit the boosterpack design. I'll take a look at these links later and see what I can come up with! Regards. Quote Link to post Share on other sites
tonesenna 20 Posted October 21, 2012 Author Share Posted October 21, 2012 So, here's a quick update. The shunt monitor was dropped because the dynamic range wasn't good enough to cover the range of possible discharge current. I made a search for an LDO with very low Iq and UVLO to avoid relying on the battery's own protection circuit and stay on the safe side. I couldn't find a suitable part, so I decided to add a voltage supervisor. In terms of low power operation I expect the rocketfuel to behave quite well: LDO's Iq is 8uA@150mA and 0.5uA@0mA Supervisor Iq is 0.5uA @ Vbat=5V BQ2057 BAT pin leakage is 1uA typical Summing all up, the battery drain with no load is expected to be around 2uA, which seems pretty good to me. I'm also changing the design to use these batteries (eiher 400mAh or 850mAh) http://www.tinkersoup.de/product_info.p ... 1576b2246a Where can I get the pinout for the connector? Is it standard? I can't find the information anywhere. Rgds, --to Once I update the design I'll post pics here. LariSan 1 Quote Link to post Share on other sites
bluehash 1,581 Posted October 21, 2012 Share Posted October 21, 2012 It's a standard JST 2 pin connector. See documents: https://www.sparkfun.com/products/8484? Quote Link to post Share on other sites
tonesenna 20 Posted October 22, 2012 Author Share Posted October 22, 2012 Yup, I know the connector's P/N and landpattern. My doubt was related with the pinout itself, Which doen't seem to be documented anywhere. For instance, the 400mAh shows the datasheet here: http://dlnmh9ip6v2uc.cloudfront.net/dat ... 400mAh.pdf On page 10 you'll see depicted a 3 pin JST connector that includes the NTC terminal. However, the product page shows a battery with a 2 terminal connector. I managed to figure out the pinout looking at the pictures on this tutorial: http://www.sparkfun.com/tutorials/241 I don't know if anyone from sparkun reads this forum, but It'd be nice if these folks fixed the documentation for these battery packs. Currently I'm reviewing the board layout. I hope I can share it soon. -- to bluehash 1 Quote Link to post Share on other sites
tonesenna 20 Posted October 24, 2012 Author Share Posted October 24, 2012 After moving the battery to the bottom I changed the whole layout. The battery charger was placed primary battery holder, so that in case I want to build a non-rechargeable version, the non-mounted components stay hidden, for a better visual effect. The PCB still needs test points and artwork. After some review It'll be send for prototyping. I was considering producing the board at eurocircuits. Do you guys have any other suggestions? -- to bluehash 1 Quote Link to post Share on other sites
bluehash 1,581 Posted October 24, 2012 Share Posted October 24, 2012 If they are quick at sending boards eurocircuits are good. We use SeeedStudio here in the forums. 10 boards for 5x5.. but I see your one side is 5.7cm. It takes around 3 weeks for the boards to reach you. Also,... like I mentioned to traxman for his motor boosterpack.. feel free to request a sponsor(RFS-http://www.43oh.com/forum/viewtopic.php?f=35&t=1825&p=12719#p12719). I'd love to put this on the Store if you want. Looking forward to this. tonesenna 1 Quote Link to post Share on other sites
tonesenna 20 Posted November 2, 2012 Author Share Posted November 2, 2012 Things have been advancing slowly but steadily. I made a major review so that I can source all components from the same distributor. I also tried to improve power dissipation around the pass transistor so that I can keep operating temperature within reasonable limits. So, here it is, hopefully the last design iteration of the rocketfuel boosterpack. Top Layer Bottom Layer Silkscreen --to Automate, bluehash and Philipp 3 Quote Link to post Share on other sites
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