inverting power supply current issue

[manjunath]

Hi all ,
        I am using mc330063A IC to get negative power supply of -5V and also i need 1A of current , the respective circuit that i am using is in attachment , in this circuit i am getting -5V but if i insert any load resistance above below 500 ohms , the -5V getting decreases to -1.2V. Here i need atleast  0.5A of current . According to datasheet it supports upto 1.5A. Can anyone help me out to get 1A of current out of this circuit.


Thank you.....!!!!

[mariush]

You misread the datasheet.  The chip supports a peak switch current of 1.5A, which is not equal to the output current.

With 6v input, the best it can probably do is about 0.3A.  To get close to 0.5A, you'll need to up the input voltage to 12v or more, or use another inverting regulator.

See below, and feel free to download the mc34063 universal calculator from sourceforge to play with numbers

[manjunath]

oh..!!!!can i get -5V/1A output voltage and current using mc340063A ..?? or is there any circuit u know ..??


Thank you

[mariush]

Without some "hacks" like using external mosfets, I doubt it.

Something similar to mc34063 or mc33063 would be these, with switch current limit from 3A and up ... but even then you can't get -5v @ 1A from 5-6v .. for that you'd need a switcher capable of around 5A switch current, and those are expensive (think 5-10$ a piece):

3.4A switch current is enough to do -5v @ 1A if you have at least 9v at the input. 3A would work with 12v and higher.

ncp / ncv 3163 (3.4A but hard to solder on pcb) : http://www.digikey.com/product-detail/en/NCP3163BPWG/NCP3163BPWGOS-ND/1434719
MC33166D2TG (3a) : http://www.digikey.com/product-detail/en/MC33166D2TG/MC33166D2TG-ND/1479117
MC33166TG (3a)  http://www.digikey.com/product-detail/en/MC33166TG/MC33166TGOS-ND/919018

MC34166TG (3a) : http://www.digikey.com/product-detail/en/MC34166TG/MC34166TGOS-ND/919095
MC34166TVG (3a) : http://www.digikey.com/product-detail/en/MC34166TVG/MC34166TVGOS-ND/919096

MC34167TG (5A) :  http://www.digikey.com/product-detail/en/MC34167TG/MC34167TGOS-ND/919097

Note that the internals of these regulators are very similar to the MC34063 or MC33063 so the formulas should be similar as well and not hard to figure out. Pay attention to maximum frequency, pay attention to components... it's VERY IMPORTANT to use proper inductors and diodes (that have the parameters recommended by formulas, or better) and the whole circuit may not work on breadboards, you may have to actually put it on a pcb to work right.

[manjunath]

TPS62150RGTR

TPS54060A

MC33063A
MC34063A


i have these IC's from which one can i get -5V /1A current ..??



Thank you

[manjunath]

what should i have to do to get -5V/1A from mc33064A or mc34063A .... ?? please give some solution for this problem.





Thank you,

[mariush]

Magic, that's what you should have.

Please understand that those chips have some limitations, a component inside can only handle that 1.5A of current.
 
To get around that, you would need to use additional components like mosfets for example, but if you can't go and buy one of the regulators I recommended, I doubt you're going to go buy the mosfets required so why should i waste time showing you anything?