+/-5v from single Li-ion battery

[ecotack]

A little off topic, not torch related, but still...

I need to produce +5v and -5v from a single Li-ion battery. Commercial DC-DC converters only come in 3v3 versions with an input range of +/-10%, therefore the possible 4.2v from the charger is to high.

I've used the LTC1624 before for a SEPIC PB charger and although it will do boost and invert the data sheet suggests it may struggle when the battery drops below 3.5v.

This is for a measurement application so ripple on the +/-5V lines needs to be minimal.

Any suggestions.

 

[VidPro]

anyvolt is this littel tiny curcuit that is adjustable that will take a wide variety of input voltage (even these low ones) and output a wide variety of voltages as adjustable with 25turn.
but because it has some common pins, it still wouldnt magically do the -5 without say 2 of them and 2 batteries.
its like a micro bench power supply, that will run on anything.

i just think it is kinda cool, really fun, low efficient, and very expencive.
http://www.google.com/search?num=100&hl=en&lr=lang_en&tbs=qdr:y%2Clr%3Alang_1en&q=anyvolt+micro&aq=f&aqi=g2&aql=&oq=&gs_rfai=&pbx=1&cad=cbv#q=anyvolt+micro&hl=en&lr=lang_en&tbs=lr:lang_1en,shop:1&prmd=ivs&source=univ&tbo=u&ei=seitTLjULJD2swOl9aSzDA&sa=X&oi=product_result_group&ct=title&resnum=1&ved=0CD4QrQQwAA&fp=102cd7f3589c676f

http://www.rcdude.com/servlet/the-353/Dimension-Engineering-AnyVolt-Micro/Detail
PDF

i suspect that you are seeking out real electronics , not consumerish toys, but for me it got stuff done in one.

here seems to be stuff that will go as low as 3.3v and do 5V. :shrug:
http://www.megaelectronics.com/docs/parts/M1WA_T Series.pdf

 

[45/70]

I've used the LTC1624 before for a SEPIC PB charger and although it will do boost and invert the data sheet suggests it may struggle when the battery drops below 3.5v.

Both you guys are probably way ahead of me when it comes to electronics, but I thought I would just mention that a Li-Ion (LiCo, or LiMn) cell that is at 3.5 volts, even under a load, is about discharged anyway, unless this occurs at a relatively high current, which it doesn't sound like would be the case.

Humm. Was that a really long sentence, or what?

Dave

 

[Mr Happy]

A little off topic, not torch related, but still...

I need to produce +5v and -5v from a single Li-ion battery. Commercial DC-DC converters only come in 3v3 versions with an input range of +/-10%, therefore the possible 4.2v from the charger is to high.

I've used the LTC1624 before for a SEPIC PB charger and although it will do boost and invert the data sheet suggests it may struggle when the battery drops below 3.5v.

This is for a measurement application so ripple on the +/-5V lines needs to be minimal.

Any suggestions.

It seems like you have at least two options to consider. One option is to use separate +5V and -5 V (inverting and non-inverting) boost converters from your ~4 V source and gang them up to produce a 5-0-5 supply. Another option is to use a single +10 V boost circuit and then split this into a 5-0-5 supply afterwards.

You can find some discussion of these topics here:

http://www.eevblog.com/2010/04/08/eevblog-72-–-let’s-design-a-product/

and here:

http://www.eevblog.com/2010/09/10/eevblog-110-lets-design-a-dc-to-dc-switchmode-converter/

and maybe here: (I haven't watched this one)

http://www.eevblog.com/2010/05/29/e...lators-and-switch-mode-power-supply-tutorial/

 

[CKOD]

How much current? Are you just feeding some op-amps?

http://www.maxim-ic.com/datasheet/index.mvp/id/1530

Will give you +/- 2x Vin, just add some LDO's of your choice and you have ~10mA you can use. and available in a DIP package so its friendly for hobbiests who are scared of SMD stuff (Embrace the SMD!)

Maxim has quite a few other charge pump doublers and inverter/doublers (seperate, not both in one package) if your application is more current hungry then that.

 

[ecotack]

Thanks for the replies.

The +/-5v will run a DAC, ADC and a power op-amp. The output current of the op-amp can be limited to what components I can find, but in our basic mains powered versions we use +/-350mA (we have made a 50v 50amp version before). I'm aiming for +/-200mA.

I've been looking at some bought in modules, ordered a couple to test. Both came on Friday, so I'll test to destruction tomorrow. One is a Murata Power Solutions NDTD0505C, its a 5v to +/-5v 3 watt convector, but will still work down to 3v reducing its output to 2 watt. The other is XP POWER ISF0305A, only 1W and 3v3, so charging potential may blow it.

Choosing a battery charger IC was a pain, there are so many of them. In the end it came down to what I can solder in my toaster oven, which was a MAX1811(easy) or LTC4064(I need glasses). Both use 5v, with the MAX1811 having a 100mA and 500mA option for USB charging, but the LTC4064 will do 1A.