http://forums.leaflabs.com/topic.php?id=1495 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:15:24 +0000 http://bbpress.org/?v=1.0.2 q http://forums.leaflabs.com/search.php http://forums.leaflabs.com/topic.php?id=1495&page=2#post-9941 Wed, 28 Mar 2012 05:50:38 +0000 siy 9941@http://forums.leaflabs.com/ <p>@bulmer, I saw mentioning of some online tool related to this IC, but in fact for most cases this is not necessary - datasheet for this IC mentions a lot of possible configurations with pre-calculated component values. One with 12V input and 3.3V or 5V output should fit our needs just fine. </p> http://forums.leaflabs.com/topic.php?id=1495&page=2#post-9940 Wed, 28 Mar 2012 05:28:23 +0000 gbulmer 9940@http://forums.leaflabs.com/ <p>siy - you said the magic words "NCP3170. This IC about 1/4 of the price of LM2734Y" :-)</p> <p>The LM2734Y is a bit more than double the price of NCP3170 at Farnell. RS don't sell the NCP3170<br /> If it is a daughterboard, I don't mind if it gets bigger. Is there an online design tool for the NCP3170? </p> http://forums.leaflabs.com/topic.php?id=1495#post-9939 Wed, 28 Mar 2012 04:51:41 +0000 siy 9939@http://forums.leaflabs.com/ <p>@gbulmer, I've not used this IC beside separate experimental board. I can send you calculated schematic and Eagle layout for that board, if you're interested. Also, while LM2734Y looks very interesting, it is quite expensive (at least in local stores) comparing to other IC which I'm going to try - NCP3170. This IC about 1/4 of the price of LM2734Y in local stores and capable to source up to 3A. It somewhat larger (SO-8 vs SOT-23), but requires smaller inductor (4.7uH vs ~18uH). </p> http://forums.leaflabs.com/topic.php?id=1495#post-9932 Wed, 28 Mar 2012 03:43:01 +0000 gbulmer 9932@http://forums.leaflabs.com/ <p>siy - Are you planning to publish a schematic, or is it better to go to TI Webench? </p> <p>A small 'switcher' may be a handy add-on for existing Maple boards; I think I remember three different people who have blown regulators.</p> <p>Were you using the LM2734Y with a microcontroller, or was it a different project. If it was STM32, did you use a linear regulator for the analogue power, or take it straight from the LM2734Y? </p> http://forums.leaflabs.com/topic.php?id=1495#post-9926 Wed, 28 Mar 2012 00:03:19 +0000 siy 9926@http://forums.leaflabs.com/ <p>To achieve smallest possible consumed space I've used 0402 resistors and smaller value capacitors. Capacitors at input/output were 0805. I don't remember exact part number for inductor, something like CDRH3D28 or CDRH4D28 from Sumida. Using all 0805 resistors/capacitors would not affect consumed space significantly. As I've mentioned design can be done with Webench and it suggests particular part numbers depending on required parameters and preferences (board space/price/efficiency). </p> http://forums.leaflabs.com/topic.php?id=1495#post-9923 Tue, 27 Mar 2012 18:00:15 +0000 gbulmer 9923@http://forums.leaflabs.com/ <p>siy -<br /> <blockquote>... I've experimented with LM2734Y (with lower switching frequency) and it performed very well. Entire regulator consumes board space comparable to space consumed by linear regulator and it capable to source 1A </p></blockquote> <p>What size components are you using to fit it into a small space? You seem to have it smaller than my estimate. </p> http://forums.leaflabs.com/topic.php?id=1495#post-9911 Mon, 26 Mar 2012 18:21:43 +0000 siy 9911@http://forums.leaflabs.com/ <p>Seems I was wrong about Discovery boards, only VL uses 1117, others use smaller regulators. Anyway, the 1117 is quite common, although it is far from the best ones. Mentioned above LM2937 is much better, it has typical drop out only 0.5V. In cases when input voltage range is narrow (less than 7V), I prefer LM3940, which especially designed for 5-&gt;3.3V regulation and capable to source 1A. </p> <p>As for switching regulator, I've experimented with LM2734Y (with lower switching frequency) and it performed very well. Entire regulator consumes board space comparable to space consumed by linear regulator and it capable to source 1A in wide range of input voltages. I've calculated schematic for 5-15V range, for example. Also, TI provides online design tool (Webench) which simplifies design a lot. </p> http://forums.leaflabs.com/topic.php?id=1495#post-9903 Mon, 26 Mar 2012 08:42:36 +0000 gbulmer 9903@http://forums.leaflabs.com/ <p>siy - yes, very important point about protecting USB VBUS line. </p> <p>I have diodes on all (two:-) voltage input lines (USB or header).<br /> I wasn't planning on removing the USB VBUS diode.</p> <p>I am looking at (low-cost) ways to supply power from the header.<br /> I'd like to run with 4 NiMh AA (or AAA) cells, which is nominally 4.8V, but dips with motor load.<br /> The 1117 has a 'spec' which says drop out is 1.1V (or even 1.2V) drop out.<br /> So 4.8V - 3.3V -1.1V doesn't leave much headroom for a diode and a battery voltage dip under motor load.<br /> Pete (micromouseonline.com) says folks have had problems with micromice where power dips have caused processor reset.</p> <p>Also, because of the design of my board, I am trying to find a through-hole regulator to put 'on the back'.<br /> I'd like it to be capable of supplying 500mA from any voltage from 4.8V upto 9.6V.<br /> The best idea so far is to either:<br /> a. use two regulators, one to reach 5V, then a second to get down to 3.3V (cheap, simple, and easy for folks to vary), or<br /> b. use a 'switch mode power supply'.</p> <p>Option a. adds even more voltage drops, or two Vinput pins (confusing).<br /> Option b. seems to require quite a lot more design, which may put folks off using a design and messing with it, and harder to get parts. </p> http://forums.leaflabs.com/topic.php?id=1495#post-9899 Mon, 26 Mar 2012 07:35:33 +0000 siy 9899@http://forums.leaflabs.com/ <p>@gbulmer, if board has enough space, then definitely more powerful regulator is better. I think LM1117 (and several clones) is one of the very common and popular parts, despite the fact that it is not the best one in its class. Many (if not all) versions of Discovery board for different MCU's use it as well.<br /> About diodes. I'm using diodes in all my boards even if regulator has reverse voltage protection (for example, wonderful automotive grade LM2937 can protect not just from reverse voltage but also from +60V/−50V(!) load dump transients). In fact these diodes are necessary not just to protect board and regulator, but also to decouple external power supply and USB VBUS line. I think this function is even more important than protection of board itself, especially taking into account that external supply can have much more than +5V. </p> http://forums.leaflabs.com/topic.php?id=1495#post-9897 Mon, 26 Mar 2012 06:46:55 +0000 gbulmer 9897@http://forums.leaflabs.com/ <p>Should we try to use a similar regulator? </p> <p>Having commonality on parts would help folks to DIY, and we would accumulate experience faster.</p> <p>Does that also protect from reverse voltage, or is a diode still needed?<br /> (I can't see any mention of reverse voltage protection on an EXAR part, which some regulators have) </p> http://forums.leaflabs.com/topic.php?id=1495#post-9863 Fri, 23 Mar 2012 15:18:42 +0000 siy 9863@http://forums.leaflabs.com/ <p>@feurig, yeah, I've also added x1117 to last version of my Mini48U (Maple Mini clone). </p> http://forums.leaflabs.com/topic.php?id=1495#post-9861 Fri, 23 Mar 2012 14:50:37 +0000 feurig 9861@http://forums.leaflabs.com/ <p>Funny I was just revising our maple mini design with a x1117x regulator (900ma) design since the wireless module we are using draws 250 ma when talking. </p> http://forums.leaflabs.com/topic.php?id=1495#post-9858 Fri, 23 Mar 2012 04:10:47 +0000 juzza_s 9858@http://forums.leaflabs.com/ <p>@feirig and @siy: thanks for the response. At least I now know that I'm not going crazy with reading the documentation. :-)</p> <p>It sounds like the code sample for pwmWrite() is still perfectly valid for the Mini. How do I go about submitting a change request to add a note for this on the pwmWrite)() document page? </p> http://forums.leaflabs.com/topic.php?id=1495#post-9857 Fri, 23 Mar 2012 02:48:32 +0000 siy 9857@http://forums.leaflabs.com/ <p>@juzza_s, you're right, LED pin on Maple is not PWM capable (same is true for Maple Native and Maple RET6 edition). But at Maple Mini LED pin supports PWM. Actually this is the main reason why my Mini64 board has two LEDs - one connected like in Maple and other connected as in Mini. IMHO, in list of design flaws of original Maple lack of PWM support at LED pin, probably, should be right after weak voltage regulator. </p> http://forums.leaflabs.com/topic.php?id=1495#post-9855 Thu, 22 Mar 2012 19:07:41 +0000 feurig 9855@http://forums.leaflabs.com/ <p>on the other hand the use of pin 13 which is the serial clock for the spi used in the arduino's ISP is subsequently also the serial clock on spi1 for the maple and maple ret6<br /> So it makes sense that it would not be pwm capable. Again we suffer the arduino compatibility here. </p>