Question about part (voltage regulator: ROHM BA50DD0T )

Hey gang-

I have been slowly researching some replacement voltage regulators..

In my breadboard/prototype set-ups.. I have just been using a good old LM7805 voltage regulator (linear)....etc.

However.. I know in the end I will have more leds (Neopixels).. then in my current prototyping set-up... an hence will need more than the 1A the LM7805 regulator can provide.

I understand linear regulators waste any over voltage from the source as heat.. I understand that while a switching regulator or some sort of Step-up/down convertor might be best.. (but also more involved)..

While there might be upwards of 1.5A for the led string... this will only ever be on/in use for a short period of time... (literally seconds at best).. so I'm hoping heat is no longer a concern.

I found this:

ROHM BA50DD0T LDO voltage regulator..

Seems to be an exact same pinout as the LM7805 as well..

However... I am to clear on a few things.

1.) Looking at the data sheet.. I cant seem to grasp HOW this is supposed to be set-up in its most basic form? Am I to be looking at page #13? and that first diagram? (I/O equivalence circuit)??? That looks to be a lot of extra components for this regulator? (I guess I was looking for/expecting something easier to implement? Like it only needed a few caps or something??)

2.) The specs on this also has me confused... (hoping someone can explain to me in terms that make more sense?)

  • it says LDO, but I'm not clear what the voltage drop is? 0.1v @ 1A? so would that be 0.2 @ 2A then?

  • If this is a FIXED (not adjustable regulator).. +5v output.... how can it take INPUT voltage anywhere from +3v - +25v?) How can I supply this with only +3v? and get +5 from the output?? That seems like a step-up/boost converter?

If I did in fact only supply +3v input.... what would my current output be? I'm leery of this. I want a stable +5v and as close to 2A output as I can get.. but this input voltage acceptance of only +3v has me questioning it?

I was planning on using a +7.4v li-ion pack initially, and thought if I could get a LDO regulator... I would perhaps also allow the use a +6v battery pack.. but this seems to make me think that I can also use a single cell +3.7v li-ion battery?

I'm looking at the through hole - TO-220-3 package...

Question about Eagle/implementation... If you place this part in Eagle... does the footprint/silkscreen displayed account for the part to be bent over/laid down on the pcb? Or is it supposed to be standing vertical/straight up?

(I'm hoping for the former so I can bend it over, and place it between 2 female header rows.)

I'm not pro at Eagle... but I have only ever used SMD parts... never any through hole parts before..

post a link for your neopixels

1: I/O equivilence is for modeling a pin in simulations. The minimum circuit is shown on the next page - looks like a couple of caps and maybe a resistor. Be sure to read all the text - that's a rather lousy datasheet IMO; most regulator manufacturers give you a design that you can copy directly, but they don't make it quite as simple.


Dropout is specified in Electrical Properties table, under "dropout voltage"

It can't, the input voltage must exceed the output voltage by the dropout voltage. It is not a boost/stepup converter. That's the minimum voltage it requires to function at all, not the minimum voltage it needs in order to generated the spec'ed output voltage - you still need enough headroom for the dropout voltage.

You need 5.7v to get 5v out with the DD-series part at 2A.

re: eagle, eagle doesn't care if it's bent over, but you need to make sure there will be enough cooling; often these are attached to a heatsink.

From page 5 "Vcc=Vo×0.95" so 5 volt regulator may drop out at 4.75 volts, see also on page 10-12 the data for 5 volt regulator

Page 13 is showing a basic 'internal' schematic of the regulator itself


uumm… ok?

I have currently used/been using a Neopixel strip (Adafruit)… as well as a DotStar leds strip (also from Adafruit),…with only a the first 8-12 pixels in use…

… and am currently testing with a NeoPixel ring (8 leds)…
But in the end… I will be using 2 x of these: (24 led Neopixel rings)

Color(s) in use will only be red and some green (to make an orange color)… this is then faded in/out…
So (roughly) 40mA tops for 48 leds 1920mA… (if they were BOTH fully on, they will not be)…
also this top current rating would only ever be ‘on’ for a few seconds at a time… not running this this high of current for long periods of time or anything.

I mean I’m not pro at reading datasheets anyways… but this one was WAY more difficult fo rme to try and get any ‘facts’…

I’m still not 100% clear on what disgram I am to follow here?

The next page (14) has a small diagram to the left (Fig.32 Output Equivalent Circuit) Is this the eone you are referring to?

  • Not sure what ZZZ/TTT means? Btut I see a 22uF cap on the OUTPUT only?
  • On page 15…(Operational notes) I see other diagrams… but different scenarios?
    I even tried to googl ejust a simple wiring diagram for this part… but didnt find anything… (bummer)

THANK YOU for clearing up the input voltage issue. (To me at least) it is VERY misleading to put +3v as the min. input voltage… if it wont do anything…or give the fixed output. So (while not the best) in theory a +6v pack will in fact work (but probably not for long)…

Re: Eagle… thank you. I understand it doesnt ‘care’… but if the footprint/silkscreen made to save/allocate the space for it to bent over?

Looks like it is? (but I have only even used SMT parts before… so going to through hole has its own unknowns for me!) LOL

I have a schematic I am close to posting for review/critique… need to wrap up some loose ends and and some polyfill/planes…etc

Hi, Have you googled PCB mount power supply module converter

Tom.. :)

Thanks TomGeorge

I have not.

(didnt even know it was a 'thing')

I have now though...

And the results are 'black box' looking objects.. is this correct? (and they do NOT look cheap!)..

Also how big are they? (they look huge!) Is this really something that is needed? (the replacement I posted wont 'cut the mustard'?) :) Knowing it wont be on (leds blinking around) for not more than a few seconds?

I'll read about these once I get home form work..

Thanks! -Gerald

Yes, my personal Eagle library has a few variations of devices standing vertical or laid over on the PCB. The same device can have many footprints. The schematic symbol is the same.

I've never found an option to "select different footprint for this device" but after adding it to the device in the library (and updating the library in the editor) then I do a "replace device" on either the schematic or PCB.

Thanks!.. So the part I have shows a full silhouette outline of the part (as if it was laying down on the PCB and you are looking down, on top of it from looking down at the pcb.)

So I'm hoping that means it a 'laydown' type of footprint.. (although as mentioned I could just bend it.. but would be nice to have the silkscreen on the board.. as well as in Eagle so I know where to NOT lay some traces.)

Now I just need to be clear on HOW to wire it up... the datasheet is kind of awkward.. (I mean not great at always understanding everything in a datasheet to begin with, but normally I fudge my way through to find the diagram I need).. this one.. not so much? LOL

  • Side question..
  • is it -ok- (acceptable) to also bend over through hole capacitors? I'd like to be able to do the same thing I am doing with the voltage regulator.. and bend it over.. so it can fit/sit between two female header rows...... and eventually be covered by the boards that will plug into these header rows.

I'm hoping to lay some final traces.. and post the schematic/board files for review as well..

(probably a new thread for that I suppose)

I -think- according to page #14 now... that it ONLY needs a 22uF cap on the output??

If you bend over a capacitor, put a blob of glue under it. You need to support the weight of the cap against vibration.

*Is that because your saying of the leads/wires breaking after some 'vibration/abuse'? Or is this adress another issue when bending caps over?