Jellybean dual output DC DC converters? - Page 1
Forum section: electronics / projects

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 28, 2018, 10:52:23 am
content: So, for a battery operated system (3 to 9V) what are the most used DC-DC converters that give + - supplies (+-10..+-15V, with less than 100mA) and low noise???I know that there are lots, last week I opened a fluke equipment and it had a MAX1675 for positive and a ICL7660 for negative....but I never know if I'm missing something that 'everyone' is using

author: spec
author_rank: Frequent Contributor
timestamp: November 28, 2018, 07:09:18 pm
content: Hi MT,Not sure what the chip is, but this is quite a common module to give +&- supplies:https://www.google.co.uk/search?q=DC+to+plus+and+minus+supplies&tbm=isch&tbo=u&source=univ&sa=X&ved=2ahUKEwiYp6aS4_feAhUIa8AKHfQmDQAQsAR6BAgEEAE&biw=1333&bih=602#imgdii=mnz4uwgs7CiHwM:&imgrc=Zfs9VCGQI7xbgM:

author: technix
author_rank: Super Contributor
timestamp: November 28, 2018, 07:20:28 pm
content: I have some personal favorites but I am not sure if my favoritism is universal:* Liberal use of TPS562200 family of 2A adjustable single-output DC-DC buck converter,* Liberal use of LP2985-family of 50mA/150mA/300mA single output LDO regulator,If your battery doesn't go over 5V, you can also use:* Liberal use of LM3671 family of 600mA fixed and adjustable single output DC-DC buck converter,* MP2212 adjustable dual output DC-DC buck converter,Or if you use a Li-po, have a MCU or other type of CPU, and need a few different power rails:* X-Power AXP209 microprocessor PMIC

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 28, 2018, 07:24:57 pm
content: Quote from: spec on November 28, 2018, 07:09:18 pmInteresting, that seems like a boost converter for the +, and a charge pump for the -. Probably a chip sold in lcsc. That solution lowers emi, since only one branch is switching but regulation in the negative branch is bad.

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 28, 2018, 07:33:12 pm
content: Its probably a AP3012, pinout matches the picture traces, and there seem to be some chinese knockoffs

author: spec
author_rank: Frequent Contributor
timestamp: November 28, 2018, 11:27:59 pm
content: Quote from: MasterTech on November 28, 2018, 07:33:12 pmQuote from: MasterTech on November 28, 2018, 07:33:12 pmHmm, good bit of deduction.I hadn't thought about a charge pump for the negative rail.You can't get much more jelly bean than an AP3012.What is your objective, to get a solder-in module or to have a standard set of components to incorporate into your PCB layouts?If the latter, perhaps use two AP3012s, one for the positive power rail and the other for the negative power rail. (assuming that the AP3012 can be configured for negative OP- I haven't checked)https://www.diodes.com/assets/Datasheets/AP3012.pdf

author: spec
author_rank: Frequent Contributor
timestamp: November 28, 2018, 11:47:40 pm
content: The AP3012 has only got a current sink output so it can't be used easily with a choke to generate a negative supply rail. A 1:1 choke would be required and a bit of jiggery pokey with the feedback, but it still looks doable.Another approach maybe be to use an external PMOSFET.

author: spec
author_rank: Frequent Contributor
timestamp: November 28, 2018, 11:57:27 pm
content: Quote from: technix on November 28, 2018, 07:20:28 pmInteresting listIt's a very good design approach to have a bag of favorite devices that you know inside out. It makes parts holding easier and takes some of the risk out of design.Thought you would like to know that the MP2212 has now been replaced by the MP2316, which does not require the bias voltage.https://media.monolithicpower.com/document/MP2212_r1.01.pdfhttps://www.monolithicpower.com/pub/media/document/MP2316_r1.11.pdf

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 29, 2018, 12:34:15 am
content: The solution to use largely depends on your requirements. There is no universal answer to this one.Some of the points to consider: max output current? Isolated or not? How low should be "low noise"? Do you really need voltages higher than +/-Vbat or even +/-(Vbat/2) ?If +/-(Vbat/2) is adequate, implementing a virtual ground is a popular approach, it's simple and if done properly, adds little noise. The TLE2426 (http://www.ti.com/product/tle2426) is a great device for instance (up to +/-20 mA). Of course there are numerous such ICs, and you can also implement that with an opamp (as long as it can source and sink enough current for your application, but you should be careful about stability).If +/-Vbat is OK, you can use an inverting regulator (charge pump or an inverting buck/boost) to generate -Vbat.You can also consider the following parts depending on the input voltage requirements:http://www.ti.com/product/tps65130https://www.analog.com/en/products/ltc3260.htmlYou can also consider using isolated DC/DC converters such as this:https://power.murata.com/en/mev1d0512dc.htmlThose tend to be a bit noisy though, so you'd have to take appropriate measures to lower noise.Absolutely not exhaustive.Another (obvious?) solution to use, but not necessarily practical or low-cost depending on the application, is using two batteries in series (that can be followed but LDOs if needed). For audio stuff, this is often the lowest noise of all.

author: spec
author_rank: Frequent Contributor
timestamp: November 29, 2018, 03:45:14 am
content: UPDATE 2018_11_29Quote from: SiliconWizard on November 29, 2018, 12:34:15 amI've used similar Murata converters and found them to be very reliable. There is the noise issue to sort, but Murata give guidance on that. Murata power modules were rather expensive for this application at one time, but the price seems to have dropped.The isolated, MEV1D0512DC (+-12V @ 42mA), which you mention, and MEV1D0515DC (+-15V at 33mA) both operate from an input voltage of 4V5 to 9V and cost around £6.36UK. They come in a DIP14, package, which makes them dead handy to use.https://power.murata.com/datasheet?/data/power/ncl/kdc_mev.pdfThe NDTD0515 may be the best choice for a general go-to converter from the Murata range of 5V to +-15V isolated modules: input voltage range: 4V5 to 9V, output voltage: +-15V at 100mA, case size, W32, D15, H7mm, cost: around, £16.73UK.https://power.murata.com/datasheet?/data/power/ncl/kdc_ndtd.pdfThe MCM6D0515C may be a good choice if you need more output current. It is isolated, operates with an input voltage of 4.5V to 9V and generates +-15V lines at 200mA each. The size is W32, D20, H11mm, and the cost is around £21.00UK.https://www.mouser.co.uk/datasheet/2/281/kdc_ncm6-775720.pdfhttps://power.murata.com/en/products/dc-dc-converters.html

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 29, 2018, 06:58:28 am
content: Quote from: spec on November 28, 2018, 11:47:40 pmThe schematic goes like this, only 2 more diodes and 2 caps are needed,http://www.seekic.com/circuit_diagram/Power_Supply_Circuit/POSITIVE_AND_NEGATIVE_VOLTAGE_SWITCHING_SUPPLY.html

author: spec
author_rank: Frequent Contributor
timestamp: November 29, 2018, 08:33:37 am
content: Quote from: MasterTech on November 29, 2018, 06:58:28 amNice findShame the LT1170 (5A)(£10.22UK), LT1171 (2A5)(£8.54UK), LT1172 (1A25)(£4.52UK) are quite so expensive, as AD (LT) components normally are.https://www.analog.com/media/en/technical-documentation/data-sheets/117012fi.pdfDo you recon that the architecture of the ebay +- output rail module is the same? It would make sense because the seller implies that the magnitude of the negative supply rail is one diode drop less than the magnitude of the positive supply rail, which I think is the same for the LT1172 circuit? I would guess that D1 (1N4148) is used instead of a 1N5819 Schottky diode, as used elsewhere, to try to make the magnitude of the +- supply rails closer.If that is the case, it makes the ebay module more attractive than if it used a charge pump for the negative supply rail.

author: spec
author_rank: Frequent Contributor
timestamp: November 29, 2018, 10:21:25 am
content: Just been looking at another of SiliconWizard's chips. The swinging capacitor LTC3260 looks useful, with built-in +&- LDO regulators giving 50mA. It is low-noise too.https://www.analog.com/media/en/technical-documentation/data-sheets/3260fa.pdf

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 29, 2018, 10:27:06 am
content: Quote from: spec on November 29, 2018, 10:21:25 amIt is a very good solution , it just needs a boost from 3V to 15V if using 2 AA batteries

author: spec
author_rank: Frequent Contributor
timestamp: November 29, 2018, 01:41:46 pm
content: Quote from: MasterTech on November 29, 2018, 10:27:06 amLet us know how it performs- I would be very interested.

author: hun_yeti
author_rank: Contributor
timestamp: January 31, 2019, 11:12:23 pm
content: I think that type of circuit would also work with AP3012, at least as far as i see, from the datasheets. Obviously you would need to adjust the values, since AP3012 switches at way higher frequency.