Portable speaker project. LM831!!!

So the goal of this project is to build portable speaker (0.5w-1w) fed by internal li-po battery and charged by USB. i will use 5v step-up converter or not depending on amplifier IC.

and this is the first point of this thread. after looking for some amplifier datasheets i found this perfect one LM831 where with 3v you can get 440 mW power output, wich is the best i've found. and with 5v you can go up to 0,9W.

datasheet :http://www.ti.com/lit/ds/symlink/lm831.pdf

the thing is i cant find it anywhere!! its obsolete and for some reason its not in market anymore...and i also couldnt find anything similar to this... lm836 is not even close to this. can someone help me here with something this good on market?

also... on ebay i found this
http://www.ebay.com/itm/LM831N-DIP-16-N-A-1-Pcs-/121129845100?pt=LH_DefaultDomain_0&hash=item1c33e6c16c

do you guys think this is reliable?? many thanks in advance

I would look at the new class-D high efficiency amps, they are designed for exactly what you are doing;



$2 for a 3W+3W stereo amp on ebay;
http://www.ebay.com.au/itm/Mini-Digital-Power-Amplifier-Board-PAM8403-Class-D-2-3W-/171192069420

many thanks for the quick reply.

thats actually very good sugestion, i was taking a look on datasheet. i want to know if its possible for this IC to connect only one speaker to it and if it has something to do with being 8ohm speaker or 2 x 4ohm speakers?? or theese are not related? bit newbie still.. :b

Edited: after some research i already figured it out, i got pam8401 for mono audio but i will keep the stereo option.

About current consumption tell if im wrong, should be
P=VI
3w/5v=0.6 A
2 speakers, so 1,2A??

Isnt this too much? Imagining im feeding them from a usb port they wouldnt work since they only draw up to 500mA..

I think im missing something here, if someone can help me out please do :b many thanks

Then.......I suggest you get a higher wattage D class amplifier like this one that has a higher operating voltage.

http://www.parts-express.com/2x8w-at-4-ohm-tpa3110-class-d-audio-amplifier-board-only--320-329

Its operating voltage is 10 to 16 volts. Just don't drive it over what your batteries can supply.

The amp that The-RB is a good way to go. The 1.2 amps that you calculated is not continuous. Its operating voltage, 2.5 to 5volts, is a good range for Li-po batteries (3.7V).

kaning said:

...
Isnt this too much? Imagining im feeding them from a usb port they wouldnt work since they only draw up to 500mA..
...

Click to expand...

That is exactly what these new low voltage amps are designed for; being powered from a 3-4v Li battery or from a 5v USB port etc.

The average amount of current it draws is based on the music type and volume. In all cases you can reduce the current the amp draws simply by turning the music down.

many thanks for both replies.. i think i will supply this with at least 1000mAh lipo battery, maybe even 1800mAh for more durability.

i was wondering about theese current consumption values because im building step up converter from scratch using mc34063 and i need to know Iout of step uo converter, in this case Iout(max) for the step up calculations. So since 1,2 amps is the maximum value they will draw i will use it as the value for calculations. many thanks

After reading pam8403 datasheet(because i want to build from scratch) i found 2 problems i cant figure out and i wonder if someone can help me.

first one is about pins. i already know for what each in is for except for PVDD ones. they are power vdd, so what are they for?

second problemi found is about LIN and RIN pins (jack pins), for Ri value on datasheet they mention an equation mentioning Ri and some Rf?? i think im missing something here because i cant calculate one without the other. many thanks

edited: Also they mention power outputs for 4ohm thd 10%, 4ohm thd 1 %,8ohm thd 10%,8ohm thd 1% but they dont mention how to get each configuration. imagining i want 8ohm thd 1% how should i proceed??

PVDD and PGND are the high current power connections for the output stage. They need big traces and decoupling caps close to them. The Vdd is a low current supply and can have smaller traces, smaller decoupling cap (as per the schematic in the data sheet.)

They, Vdd and PVDD, connect together at the battery, (they should have separate paths to the battery.) GND and PGND should be tied together at the chip with big traces.

Are you laying out a PCB?

many thanks for that, now it makes sense.

i will use the typical configuration they offer in datasheet. i just want to calculate values of Ri for LIN and RIN. About EMI (eletromagnetic interference) if i should use 1000uF cap option or ferrite bead option.

edited 1:i will but by now no, still making calculations, deciding wich components i need and making prototype.. still much to be done.
goal should be: speakers fed by li-po battery, step up 5v to feed pam8403(audio amp), lipo battery charger(mcp73831) and bluetooth module(bc04).

edited2:
As i said i want to have bluetooth module on this project. in this case the supply voltage is 3,1v min - 3,6v max, with a Li-Po battery wich can vary from 4,2v when full and 3v when empty.
for this the best would be a fixed 3,3v step up step down converter. Anyway Is there any other way to do this in more simple way? something like zener diode regulator? im not so much into zener diode regulators, but would this work?

example: 4,2v battery with 3,3v zener diode regulator. this would give a fixed 3,3v to the load and when battery gets below this value zener diode does not conduct and battery feeds the load directly right? then would only need something like voltage comparator to cut power supply when battery gets too low?many thanks

The MC34063 is the wrong IC for that job. There are tons of cheaper smaller ICs these days for 3v to 5v boost conversion.

You really seem like you are reinventing the wheel? Why make your own when you can buy a $2 module with the amp already set up?

And likewise the 3v to 5v converter, you can buy those as a cheap module already made for about $1.50 on ebay too.

If you are really fixated on making your own PCB, then just put some header pins on the modules and solder them into your PCB.

No i dont think i am reinventing the wheel, but now there is modules pretty much for everything and its like lego, where just need to connect wires. How fun is that? Also, what will i learn with this?
For instance while making my own step up converter i get to know how they work, learn new eletronic concepts etc etc. Plus is more gratifying like this.

Thanks for the tip, i will try to check some other component for step up. About zener regulator it works like i said? And tips about Ri, Rf on pam8403?

edited: i already found the answers, im ordering parts later today for the amplifier circuit thanks a lot