LE33CZ Linear Regulator: Minimum Input Voltage and Quiescent Current Consumption

Hello

I wanted to employ the LE33CZ regulator in a circuit. How much V does it need for operation? I mean the internal consumption of the components inside the regulator.

Sounds like you're asking what the _Drop Out VOltage_ is. It's 0.2V typical, 0.5V max [which is rather impressive!]

So, you would need to supply a minimum of 0.5V + 3.3V or 3.8V -- unless you're sure the environment that it will be operating in will not exceed the limits specified in the datasheet for the max 0.4V specification (Iout=100ma, Tj=25°C [not likely]), then it would be 3.7V -- BUT, you might be able to get away with less input voltage -- refer to Figure 4 and Figure 5 on the ST datasheet.

So it would be sufficient to power the regulator with 3 AAA rechargeable bateries (1,2V each = 3,6V). I don't think I will exceed the average working conditions.

I have an additional question, how can I reduce the output current from 100mV to 80mV without affecting the voltage of 3,3V? I thought about employing a transistor, but have little knowledge, how to do it. Maybe it would go with an additional resistor loop, like on the attached picture?

Its called use the web and download a datasheet Would you like someone to hold your hand as well

Maximum ratings its called

Page 5 of 22 pages

Website address

http://www.st.com/internet/com/TECHNICAL_RESO...TECHNICAL_LITERATURE/DATASHEET/CD00000545.pdf

Welcome to our so called future of so called design engineers , who produce so called imports into the country Welcome also to a record number of companies failing because so called engineers just like this one also through not looking at datasheets then fail to follow clear instructions and schematics which show you exactly how and what to observe Welcome to the worlds record failures because engineers or would be engineers just like this cant be bothered to use the net and do some research Welcome to high unemployment rates and the normal pass the buck story Welcome to third rate Britain and third rate training and a country that is no better than Uganda , Zimbabwe , Africa , India

Welcome to a country that is supposedly educated to high standards where we don’t have one single solitary company anymore because of the number companies moving to Europe for cheap labour, no quality , no standards nd leaving the UK with no education or any skills Welcome to British current and past government policies which have lead to the downfall of this country and welcome to sweet FA applauling standards and nothing but one row after another

Sorry YES ALL 1000 percent true

Sorry, but I am not living in GB. I never wanted to and I am not an engineer, but just a hobbyist, a beginning one.

But you can use the net and you can use a computer and I dare say you can download lots and lots of other applications, amongst other subjects which we wont go into , but when it comes to actually wanting to learn and be something

Aaaah that’s different not that the United States is much better at the moment from what I see and hear either seems to be a global disease this one

A hobbyist is one that is interested in his topic One that wants to make something because he / she has so much interest nothing will stop that person in pursuing that hobby Typically they want to be the best at what they do but somehow looking at this Im not so sure you do

If you were this interested the first thing you would have done is “LOOK IT UP” Thats what normal people do if they are that interested and looking at the states at the moment and some of their excruciating design work I’m am not impressed at all , I honestly thought that the US would have a lot more get up and go I was looking forward to some competitive interesting conversation

What happened !! hmmm

My American lecturers in the Uk were top notch teachers TOPS No one could ever argue that some of the best engineers id ever met similarly some of the best University lectures and the engineers from Motorola were amongst the best tutors I ever met in my entire lifetime What the hell has happened to engineering in general be that hobby or otherwise

See I don’t see to much of this around anymore I see lots and lots of mistakes and catastrophic eras with companies that have dealt with the US but i don’t see to many success rates here I also don’t see very good communication going on either when you are supposedly the forefront in communications and I’ve spent many years in communications There was a point when I could honestly say The US knew their stuff , whats the impression you have about this then and not being able to look up a datasheet ?? Or shouldnt I ask that either

I think its quite important myself or dont you think so I thought you might have this highly intelligent mind thatv is continously enquiring seeking knowledge from all manor of literature

Perhaps it me but looking at the facts I can say I see any decent standards anymore , hmmm !! Or should Inot remark on this iether

You are shooting with an artillery gun at a bird. But aim precisely. I am just a beginning hobbyist with absolutely no background in electronics, trying to build a small circuit, just for fun. I don't have anything in common with any corporation and let's keep it that way. Socialist, by the way and not very technical oriented.

I appreciate that simon but it doesent stop you from simply typing into google does it or are you that uneducated that you cant manage this very simple task What do you do for a living Simon ? I thought the americans were the ones for shooting at targets simon without aiming correctly seeems to be a history of that as well

Lets put this another way simon what am I supposed to think when I contact people in the United states asking for thier co operation and they are big companies such as Kicker for example and five to six emails later they then advise me "Oh they are exhibiting in dallas and ill get a a salesman to contact you shortley and this doesent happen ? " Make that your fisrt question

What am I supposed to think when I then have to go back to a British company who’s representing yourselves in Britain and they ten tell me that they cant get answers from the USA and that the USA are refusing to co operate with them and five years on they just conveniently forget to advise them that there are a whole list of modifications that need to be done and haven’t been and this company has been selling over 1000 to 2000 peaces of equipment and its all coming back and they cant pay me What do i think then ?? What’s your answer to this Do you feel this is a good representation of the USA I don’t!!

Lets put this another way what would you feel if I turned these tables on some of you and put some of your American companies out of business for good in the UK which I can do Easily done you know What would you say to this

Would you feel good about this ? or Would you be a little upset with this attitude ?? What if this was your family bussiness and your homes and house and lives depended on this as your source of income What would you think then ??

I m not worried about your political upbringing as far as I’m concerned socialist, non socialist makes no difference to me its the person you are that counts That’s me quite frankly I don’t think any of this good to be fair do you What do you reckon on this subject Don’t you think people should at least make some effort

Do you possibly think I’m being funny asking you who is asking the questions to go away and at least do a very simple search Or do you think people should wait on you hand and foot Slight difference if you’re the company director and you need to pay staff to go and do this for you that’s different but don’t you think that what I’m asking you to do is beneficial in that it makes you go and look things up What would happen if we all went to school and didn’t look words up in a dictionary for example Would we be able to read and write or do you think we would Knowing the answer to this why cant you then do very much the same after all isn’t this exactly the same

There is no excuse for this is there really bar that of I cant read and write which well yes in some cases this is true In fact they have lots of people in the UK believe it or not who cant read and write , "Not joking even to this day 21st century !" , but then if that were the case you wouldn’t be on the net would you lets be honest

Some of them have never had a job Not Joking never worked in thier entire lives In fact they live like rural africans out in the bush some of them Youd be hard pushed to even begin to understand this and you would never believe me unless you saw this first hand Not Joking !! thats how serious some of this is In some cases theyve attended school for maybe 3 years if your lucky In other cases theyve never attended school athey are now 50 years plus , No skills , No job , No education and a government thats just stopped thier benefits dumped Couldnt care less attitude hmmm TRUE

Possibly you might find this acceptable I dont and thats being 100% straight forward and honest

What would you say to all this then Clever You tell me Simon

Britain dates back to the 11 century America possibly the 15 th century Africa the 18th century Why is it then that we have people living like this now in the 21 st century who have never worked , never been to school , never had a job You tell me Why have I got to have such a row with people to simply go and look something up why the arguments with some of you ?

After all isnt it you that are asking us to give you the answers Isnt it you that wants to learn Ive done my studying years ago Isnt your country that wants to trade in britian Isnt it your country that wants to sell its products in Britain so why have we got to put up with We not supplying information or technical diagrams I have to put up with this situation in Britain as well make no mistake and I dont find this acceptable either So why should I put up with this from the USA maybe you can go and ask your president of the USA why we have this attitude



So why so many arguments with some of you

Think of this another way Simon what if poor old Ruby wax had to pay Britain a brief visit and what If Simon I dint like this non co operation story and I decided Nope I’ve had enough of this Time to put Ruby wax into HM prisons You wouldn’t be too happy would you and you see Simon I do ever so like Ruby Wax I do but unfortunately Simon I have to support British concerns

You understand that don’t you Simon?? I’m sure you do and then of course there’s MacDonald’s hamburgers and I hate MacDonald’s hamburgers terrible food this and we let MacDonald’s trade here out of the goodness of our hearts to be honest I mean they could just vanish overnight No explanation just disappear That would be really terrible wouldn’t it So do you possibly think we could just have a tiny weenie little bit of co operation please there’s a good chap before terrible misfortune befalls some lovely people

Well, somebody seems to be having a bad day. I guess I'll take it upon myself to apologize for the tone here. Some people forget that we were all beginners at some point.

Don't get discouraged, Simon. I still scratch my head over some of the data sheets I run across and I've been looking at the things for 30 years.

You are learning by doing, and that's the best way.

I do regret I don't know enough analog electronics to reply to your schematic. If you ever have a question about digital electronics (and are still brave enough to post it here!) I will do my best to give you a polite, informative answer.

Keep on keeping on - Bob

I second that, Bob. I remember when I was confused about Drop Out Voltage in a regulator, so lets cut the beginner some slack.

3 x 1.2V is right on the boarder line of "typical". Now, an engineer has to consider _worst case_ conditions and typically designs to that margin, but if this is a "one off" (meaning just something you're doing for your self so it's not necessary ot be so _nit picky_), AND if you are sure that the environmental conditions won't push your regulator into the _max_ regions, then 3 1.2v batteries might be fine (but, one more consideration, what about when the cell voltages begin to droop due to discharge? 1.2V sounds like either a NiCad or a NiMH battery. Both have a fairly flat discharge curve, so you should be fine for most of the discharge capacity, but 1.1V is typically considered the cutoff point for discharge (especially for a NiMH which doesn't survive deep discharge as well as a NiCad does). so you will be somewhat limiting the duration of useable power.

Just some things to consider.

When you say output current of 100mV to 80 mV, I'm going to assume you mean _ma_. The 100ma rating is the max current the regulator is designed for, The amount of actual current will depend on the load. V=I*R (or as we like to put it: V=IR) The regulator will do it's best to supply 3.3 volts to whatever load is placed on the output (e.g. a resistor from the output of the regulator to ground). If the load has a resistance of 33Ω, then the current flowing through that resistance will be 100ma (V/R = I .. 3.3V/100ma = 33Ω). If the load has a resistance of 41.25Ω, then the current will be 80ma. If the load has a resistance of 330Ω, then the current will be 10ma.

The load regulation spec is for .5ma to 100ma (it's guaranteed to hold the output voltage to within 25mv for that current range), but this regulator has an output current limit of 150ma, which means if the load resistance exceeds 22Ω, the regulator will drop the output voltage to insure no more than 150ma flows into the load. So, if the load were, say, 10Ω, then the output voltage of the regulator will drop to 1.5V (give or take whatever tolerances are in play).

BTW, Mark -- how was Simon supposed to get what I just offered by Googling it -- what would you Google to get that particular explanation? Especially if you don't know your _mv_ from your _ma_ (not that I'm faulting you, Simon, for that mistake -- I've made plenty of mistakes like that on my way up the learning cure

Thank you for the words of encouragement:) That was a long tirade against the US...

If it comes to the discharge of the batteries, how much dropout voltage do I need to take into account? If only one of the batteries discharges to the level of 1,1V and the other two not, then I have 3,5V on the input, which is exactly the shutdown level of the LE33CZ (dropout is 0,2V). I mean, maybe the one "discharged: battery still can work with the others two still "intact"? Maybe I should choose an LDO with lower output voltage (3,2V) or another one, 3,3V output and ultra low dropout (0,1V)?

I have attached a small image to show, how I wanted to manage to decrease the current from 100mA to 80 mA. My leds have a forward voltage of 3,2-3,5V and input current 20mA each. There are four of them. I have found really a simple way to reduce the current without affecting the voltage, with a FET transistor. There is a resistor built in, do I really need i? If yes, how should I calcultate the resistance? According to:
http://discuss.biohack.me/discussion/250/new-tdcs-regulator-designs/p1
it is called a bias resistor:

"Basically, the current through the resistor creates a negative potential at the gate (law of ohm, V = I * R, so a current of 2 mA through a 100 ohm resistor biases the gate by -0.2 V), and if it gets lower than a certain threshold value, the gate slams shut.
I'm using BF245C myself, but any depletion-mode JFET with an appropriate gate-source threshold voltage will probably work."

That’s ok Steve I agree lets cut this person some slack, but lets also make the request a beginner be a beginner and that means look up a datasheet, or at least, download a datasheet ,or ,should I also classify some of your US counterpoints who are running corporate companies in the UK with just the same scenario and who couldn’t look up a datasheet further classify some of these coperate managers as beginners

Maybe thats the answer


In which case maybe we should shut them down

We just about fed up to the back teeth with being called into these companies with this problem and it is just for this problem Couldnt look up or read a datasheet Total cost to the country 150 shops and 4000 staff unemployed



No so funney is this anymore

Well you know come back with these answers and Ill start to change my attitude as well not exactly difficult request is this

Much needed if you want our oppinion !! Or if you really would like to offer this fantastic encouragment perhaps you would like to chat to Mark Rolf and some of his blokes who have been waiting nearly 3 years for a dashbourd to arrive from the USA after having paid some £3000 pounds plus who incidently also cant pay his bills on time thanks to this outrageous carry on like many other people stuck with this problem at the moment

Perhaps we should ignore this as well !!

Hmmmm ?? Perhaps you could answer that as well for me together with diagrams and whats needed to provide after sales service or is this something you think we should ignore as well Who incidently raises money for children in the Uk along side various other problems for example signatures and personall photos with David Hoffman

Thats a british hobbyist who invests some £3000 pounds in American products hes a bobbyist too but he can still look up a datsheet Or should we take that bussiness else where

Up to you !! I thought the United states were allies not enemies im beginning to wonder

I start to think that you want to sabotage my question. What is wrong with you? I have searched for the information and haven't found it, so please be productive or just stop writing your embarassing comments. No one here is interested in your attitude towards the US, this is an electronic forum, not politics. Stop this guerilla warfare, don't sabotage human efforts to learn something. Are you a saboteur? (rhetorical question) Yes, you are! So shut up and don't disturb, in Gods name!

Well, OK now... how about we not make this a US verses _them_ shall we. This is just one guy who has seen a lot of pain and feels it his duty to educate those he perceives as failing in similar way(s) as those who _caused_ his pain.

Take consonance in the fact that there are two of us here that are disagreeing with Mark's good intentioned but misguided efforts. Barking back will only conjure a dog fight.

And, Mark, perhaps all that was needed was a polite question: "Did you consult a datasheet?" In other words, rather than assuming the _worst_, how about collecting some data. Then you can respond appropriately, rather than shooting first, and asking questions later

Ah so... it's an LED you want to drive. That's different. What you need is a constant current regulator. Your JFET with resistor is such a beast (called a Current Dependent Diode or CDD), but you'll be hard pressed to get the drop out voltage down as low as you want and still maintain reasonable current regulation -- but I have little experience with this circuit, so perhaps there is a way that I don't know about).

So, question: how critical is the intensity level? Can it vary slightly, in this particular application? If so, then I would advise just using a resistor. But, even that is tricky because of the tight margins you propose. You see, an LED is a current driven device. It's actually a diode with similar properties to a silicon diode, except for a larger forward drop, and not such a predictable forward transfer curve (for a silicon diode it follows an exponential curve very well). But, the main property that they share is a small change in forward voltage for a large change in forward current. The intensity follows the current, more so than the forward voltage.

The explanation is somewhat involved, and if I have time later, perhaps I'll tackle it. In the mean time, try looking up LED forward transfer properties, Or _how to bias an LED_ or _how to drive an LED_ or even, the characteristics of a silicon diode (you are interested in the forward bias characteristics). Have in mind understanding why a current regulator is more desired over a voltage regulator for driving an LED. Also, bear in mind that a series resistor can function as a crude current _regulator_, but only if the source voltage is much higher than the load voltage -- and that a current regulator simulates a huge resistance (with the ideal being an infinite _dynamic_ resistance).

Also, because the forward drop of an LED can vary between devices (and batches), that is another reason why driving an LED from such a low voltage is problematic.

Regarding battery discharge, you want the cells to be as _balanced_ as possible (i.e. have them all discharge at the same rate), otherwise you will have cases where one or more cells drops too low in voltage or even wind up being reverse charged -- something that most battery chemistry doesn't stand up to. Discharging cells too low can be hard on them -- the extent of this varies between battery chemistry. NiCads are more tolerant of this than NiMH, but discharging to zero and especially, reversing charging, is bad for both types.

OK, I understand, that the jfet needs some additional voltage in order to operate properly? If I take for example this one:

http://www.datasheetcatalog.org/datasheet/philips/BF246C.pdf

Gate-source voltage is -1,5V, so I would have to add this value to my main power supply? I would like it to operat at its max current 80mA, so I wouldn't need a bias resistor behind source.

I just thought of another possibility for driving your LED(s) -- a Joule Thief (can drive a white LED from as little as 0.5V -- you could use just one cell!):

* http://www.evilmadscientist.com/2007/weekend-projects-with-bre-pettis-make-a-joule-thief/
* http://www.emanator.demon.co.uk/bigclive/joule.htm
* http://www.talkingelectronics.com/projects/LEDTorchCircuits/LEDTorchCircuits-P1.html (improved version)
* http://www.r3uk.com/index.php/tech-tips/43-electrical-tomfoolery/179-the-joule-thief
* http://www.prc68.com/I/JouleThief.shtml
* http://madscientisthut.com/wordpress/tag/joule-thief-schematic/

But, then, with this circuit, you run the risk of running the battery down too low.

Yes, I read about that, but the risk of damaging the batteries is too high. I will stick to the LDO with resistors or a JFET.

Mark,
Now just settle down & take a few deep breaths.
Feel better now?
OK then maybe a nice cup of tea ...............