Suitable Power Supply for Mini2440

On my Mini2440 + VGA, unfortunately, was no power supply. Can someone tell
me what requirements must be met by a suitable power supply? (Voltage,
current (power), polarity)

5v with 2A rating would be the best

Thanks a lot. I bought a power supply with 5V and about 3A. Unfortunately
the adapter doesn't fit. But I'll try an other power supply next week...

5V/2.5A powersupply damage by Mini2440 + LCD 7" Colour TFT LCD.
Now i use 5V/15A and it works fine!

Ok, about 1A or 1.5A seems to be the best choice. But I can't find any
information about the size of the connector of the power supply. The one I
bought was to big. Does anyone know the right size?

2A is minimum! More is better than less.
I have now fifteen ampere turn! If in any case exaggerated.
2.5 A is evaporated at me.
The connector should have internal dimensions of 1.35 mm.
The allocation is plus the inside and the outside negative.
The best you take the whole board with the purchase.
In the electronics store you get the right plug to solder!
Then you can use the 3A power supply.

Oh ok, I thought you forgot the dot by 15A. Thanks a lot for die info.

I tried to put 5v, 500mA. The indicator of power supply light up weakly.
but no reaction on 4 other LEDs.

Why current also needed to be consider apart from voltage??

The board does not even boot up? If you do not have enough current
capability the supply voltage will either sag below the minimum required to
run the board or hopefully go into current limit and effectively shut-down.

The mini2440 with backlight on draws about somewhere around 1Amp.  A 1Amp
or 1.5Amp supply should be just fine.  Bigger, just costs more.

The connector is a bit difficult, so make sure the power supply works with
your mini2440 and does not shut down if you wiggle the connector slightly.

Think there was another thread on the connector issue.

Good luck

Hi all, I´d like to know the plug conector name of power supply. If
somebody know, post here!

They are a fairly common DC plug connector of the type that come on plug
packs.

Measure the outer diameter with a vernier caliper and check the internal
diameter with a drill bit.  1.0mm from memory, but check it!

The main problem I had, was that the outer diameter seems to vary a bit
from manufacturer to manufacturer.  If is on the loose-side the connection
will be intermittent.

From the product page
DC-Plug: 1.35mm inner x 3.5mm outer diameter

Can I use CON4 to supply power FA?
Where is the voltage regulator of 5V (power supply VIN --> 5V)?

I assume you are talking about the mini2440.

There is no 5V regulator, that is what the plug-pack provides.

CON1, CON2 and CON3 are UART connectors and according to the schematic
(found on the downloads page) they all have a label CON4 under each one. 
There is a VDD5V pin on each one so I conclude that you could feed your
regulated 5.0V supply into one of these pins.

Doing that will bypass the power switch and your next problem will be
getting some of those connectors :)

On another connector labelled CON8 (on the top) and CON4 (on the bottom) it
looks like you access to both VDDIN and VDD5V

The Mini2440 with W35 display takes 3 watts max or 600mA. ANyone who needs
more than 2A for a 7" has some other problem.

ARMWorks has the 4 pin power cable and a matching header in their cable
kit.

Thank you davef for your answer.

Can you tell me why that VIN and VDD5V is not connected, if there is none
component who connect them?


Now, I'm working with some GPIO on CON4 using flat cable (34 wires). So if
there is no inconvenience, I will power the mini2440 with the same way :)

I believe they go to either side of the power switch, which is not on the
schematic.

A quick ohmmeter check should confirm.

A visual shows the DC power input goes to one side of the switch so leaving
the switch in the off position check, with a ohmmeter from the other side
of the switch to a VDD5V pin on any of the CONs.

Absolutely, they go to either side of the power switch.

Thank you again davef

devef >> What is the best way to protect ADC pin on CON4? I've tried 3.3V
Zener but it not cover all voltage range (0V-3.3V).

It true that the GPIO could support till 4.8V  (cf. S3C2240 datasheet, page
554)?

androjes,

Hold on a minute!  Looks like I may have been looking at the wrong CON4. 
When I did the document search I found the UART connectors which all have
CON4 on the bottom of the symbol.

I now understand you are talking about the GPIO (CON4) connector.

The traces for these various VDD5V lines to these connectors may not have
the current carrying capacity of the intended 5V power input trace. 
Measuring the track resistance or being able to view the actual sizes of
these traces would be necessary (and some of them are probably buried in
inner layers in the PCB). 

Protecting a ADC input.  I do not understand "but it not cover all voltage
range (0V-3.3V)."

On all inputs I use a 47 Ohm series resistor on each port followed by a
Bourns CD143A-SR2.8~3.3 – Steering/TVS Diode Array Series to the outside
world.

My datasheet is numbered differently than yours, ie 22-45.  Searching for
the word tolerant shows up a few hits but no suggestions than any ports are
actually 5V tolerant.  Which datasheet are you looking at?

As I recall, I think their previous part the S3C2410 had some 5Volt
tolerant inputs.

So, using CON4 to power mini2440 is not really a good idea!

>> Which datasheet are you looking at?
http://www.friendlyarm.net/dl.php?file=S3C2440.pdf

>>I do not understand "but it not cover all voltage range (0V-3.3V)."
Using 3.3V zener the output can't reach till 3.3V!

>> On all inputs I use a 47 Ohm series resistor on each port followed by a
>> Bourns CD143A-SR2.8~3.3
It's really necessary to protect mini2440 with the CD143A?

It is an idea that requires further investigation!

That is the same datasheet I have.  Ah, page 27-1 shows as page 554 in the
toolbar :)  Yep, that was one of the hits I got on the word tolerant.

>> Using 3.3V zener the output can't reach till 3.3V!

I still don't understand.  A zener diode will do nothing until the voltage
reaches 3.3V then it goes low impedance.  With a Zener diode clipping at
3.3V the voltages in the last few hundred millivolts at the top of the
input range may be affected (non-linearity).  It should have no affect
until you reach close to its zener voltage.

Sorry again, looking at my breakout board the Zener goes on the input side
of the mini2440 and the series 47 Ohm resistor goes to the "outside world".

The CD143A is really just a more consistent method than using individual
zeners.

No, you don't have to have input protection, however I was not keen on
blowing up a 3V3 input when a lot of the hardware still uses 5V signals.

We do all this protection stuff in commercial product where the environment
is probably more closely controlled than a hobbyist playing around on his
workbench.  In other words, I see it even more relevant that the inputs
have some protection.

>> So, using CON4 to power mini2440 is not really a good idea!

When CON4 was one of the UART connectors it was probably a better idea as
it is very close to the power connector and switch.  

You can see the traces to those connectors on the bottom of the PCB.  The
5V trace to those connectors and to CON5 look like they could handle a
"back-feed" setup.

CON4 has the same size trace coming from the USB connector, but must go
internal to pick up the trace to CON5.  I'd have to pull the touchscreen
off to see if it is a top-side trace.  It looks like that trace goes to
other layers by means of a single via (by the silkscreen marking R79).  It
even looks like there might be thermal relief on that via so that may
become significant contributor to overall track resistance.

Another thought ... a lot of your input power usually go to USB devices and
as the track from CON4 (GPIO) is a good solid trace to the USB connector
then that part of the total loading is removed from any traces to the rest
of the mini2440.  

The LCD and its controller is another significant load.  Where does its 5V
feed figure into the overall distribution plan?  Lastly, you would need to
consider where the 3V3 and 1V8 regulators attach to the 5V bus and take
that current loading into consideration.

Is this for commercial product?

>> Is this for commercial product?
Yes!! Especially for industrial application.
Are you confident for its robustness? do you have a ruggedized version?

>> I still don't understand.  A zener diode will do nothing until the...
I've tried this method
(http://www.thebox.myzen.co.uk/Raspberry/Breakout.html) with Resistor = 150
ohms and 3.3 zener

When I apply 2.98V in circuit entry, I measure 2.79V in output (gap=6.3%). 
when I apply 3.28V in circuit entry, I measure 2.97V in output (gap=9.4%).

This drop volt (more than 5%) is not acceptable for my application. Because
I need to measure voltage between 0V to 3.3V using mini2440 ADC.

>> You can see the traces to those connectors on the bottom of the PCB...
Yes, I think that those tracks are designed to support 5V with back-feed
setup.

> Are you confident for its robustness? do you have a ruggedized version?

Do I have a ruggedised version?  I am just a user, I have nothing to do
with the design, manufacture, sales or support.

The actual unit has proven to be quite reliable, to me.  The only issues I
have had are finding good DC power plugs and a intermittent SDcard socket. 
That is because I have probably plugged and unplugged SD cards several
thousand times by now, into one mini2440.

What you measure on the gap is precisely what I was talking about. Which
zener P/N are you playing with?  Would the CD143A-SR3.3 be a better choice?

Why do you need to measure all the way to 3.3V?  Just pot it down a bit,
say to a maximum of 3V, put the input protection on and no more problems. 
You just lose a bit of resolution.    

> Yes, I think that those tracks are designed to support 5V with back-feed
setup.

I think some of the tracks could handle a back-feed setup.  I haven't seen
how 5V gets to the USB device connector.

>> I haven't seen how 5V gets to the USB device connector.
It have!! There is a thick track from VIA next R79 (botton side) or K3 (top
side) to VIA next R41 (botton side) or SDCard socket (top side).

>> Which zener P/N
from BZX 3V3 family, but I don't know exactly its P/N.

>> Why do you need to measure all the way to 3.3V?
Measuring to 3.3V is a requirement.

Great.

Those vias look really odd to me.  Neither of them even look like they
connect to the trace, I see an annular ring around the via that looks like
the copper is etched away.  Is it just a optical illusion caused by the
silkscreening? 

The CD143A-SR3.3 or more suitable devices might have a smaller effect
around the breakdown voltage.  I didn't see any curves on the CD143A-SR3.3

> Why do you need to measure all the way to 3.3V?

I meant is, why do you need to put 3V3 on the ADC pin?

To be more explicit ... the interface to your device could have a
measurement capability to 3V3.  In your device you take the 3V3 and reduce
that say by a 1K to the input of the mini2440 and a 10K to ground.  This
way you will only put 10/11 * 3V3 = 3Volts on the mini2440 input.  3V3
zener to ground and job done.

What am I missing here?

>> Is it just a optical illusion caused by the silkscreening?
I already tested them, they are perfectly connected. I think that those
vias are also used as testpoints.

>>I meant is, why do you need to put 3V3 on the ADC pin?
I need to measure signal voltage through an OpAmp (TL082), with high
precision. The voltage range is 0V-3.3V.

In normal condition, the OpAmp can't output more than 3.4V.
Cause of opAmp power (+/-5V), the ADC pin can't receive more than 5V.



>> The CD143A-SR3.3 or more suitable devices might have a smaller effect
>> around the breakdown voltage.
My last solution is to use OpAmp in follower mode. It has no drop voltage,
but it just fairly expensive compared to zener.

>> That is the same datasheet I have.  Ah, page 27-1 shows as page 554 in
the toolbar :)  Yep, that was one of the hits I got on the word tolerant.

The ADC GPIOs are really 4.8V tolerant?

Good morning,

OK, on the vias.  I was just about to scratch off the resist to check!

It does say the VDDadc can be up to 4.8V and normally you are allowed to
take an input voltage up to its supply rail (well slightly over if current
limited). It also seems to state that normal GPIO can go to 6.5V.  Good
luck in trying to get Samsumg to confirm.  We use a lot of their parts and
I thought a had a reasonably hot-line to their support people, but could
never get anything useful out of them.  If you search "tolerant" you will
find a lot of previous traffic on this site. 

If you look through the S3C2410 datasheet I think you will find that they
are much more specific about the voltage ratings on the many different
types of I/Ps they use.

For the equipment we were making we needed to know these facts to ensure
100% reliability, well as good as reasonably possible.


Back to the ADC input:

There must be another reason why you are not scaling the input voltage to
ensure the maximum NEVER went above 3V or so. Slight lost in precision?
Precision will be limited by the number of ADC bits.

What accuracy are you trying to achieve?

>>What accuracy are you trying to achieve?
With 10 bits ADC, I'm trying to achieve 3% accuracy

I decide to use an OpAmp to protect ADC gpio, it's more simple and
reliable.

Thank you davef for your post.

You are welcome.

Accuracy ... just keep in mind the tolerance on the 3V3 reg as the ADC
reference (Aref) comes from there.

Good luck!

davef

Hi davef,

I think is not a very good idea to use a 5V power supply.

I used an on-board converter +/- 5V/1A (10W)
http://www.digikey.com/product-detail/en/RAC10-05DC%2F277/945-2112-5-ND/...
The result is not satisfied because the screen is fairly glitched.

If you check the adapter which is delivered with Mini35-OEM, it has
5.25V/2A.

How do you think when using 5.2V/1A for mini2440 + 3.5" LCD

If you check the max voltage rating on every component and they are, say
greater than 5.5V then running 5.2V will probably be OK.

One of my adapters was 5.1V so I am happy running 5.1V to it via my own
supply.

My screen doesn't glitch until the supply gets down to 4.7 - 4.8V.  Are you
sure it is not an intermittent power connector?

Getting DC power plugs that fit properly into the DC power socket has been
a "hit and miss" affair for me.  Fortunately, our electronics shop had 3
different makes of plugs in their bin so I bought several of each.

I checked the schematic to see what actually runs off he raw 5V.  It looks
like 5V goes mostly to peripheral connectors and the on-board regulators.

So, you are probably more concerned about the voltage rating of USB devices
you plug into the board.  I'd check out what the LCD controller supplies
can handle, see lcd35_schematic.pdf

Had a look at the linked datasheet.

Well specified, but I couldn't see anything that relates to transient
behaviour.  IE, how the output voltage holds-up under sudden increases in
current.

I see it can handle up to 36000F cap on the output, have you tried that to
see if it is surge current related?

>>My screen doesn't glitch until the supply gets down to 4.7 - 4.8V.  Are
you sure it is not an intermittent power connector?

My on-board adapter supplies: 4.92V/4.45V resp. off-load/loaded
And I powered Mini2440 via CON4 (34pin GPIO)

>>One of my adapters was 5.1V so I am happy running 5.1V to it via my own
supply.
Could you send me the reference of your adapters? 
I supplied 5.1V to mini2440 using DC power supply (Agilent), everything
seems OK (no glitch found). It consumed around 650mA that all.

4.45V will be a problem, all right.

The datasheet says 1.5% drop at rated load current.  That is 0.1Volt drop
from no-load.  You are only drawing 1/3rd the rated load current and the
drop is much much higher.

Something is not right here.

Did you try a big capacitor on the output as a test?

>>Did you try a big capacitor on the output as a test?
not yet, thanks for this tips

> Could you send me the reference of your adapters? 

Sorry, I did answer then went "off page" and lost it.  It is a modified
switch-mode supply out of some equipment that the company I worked for
make.  It is not really suitable for general use.

It uses a pretty common LM2592HV switcher. www.ti.com and look at the
datasheet.

hai,
     i am using an smps for mini 2440 with a voltage rating of 5v, current
2 amps..
 
in this mini 2440, i am contolling heater(upto 400 degree capacity) by gpio
pins using pwm. when the heater  reaches its 300 degree temperature  the
mini 2440 is shutting down... can any one help regarding this issue.
 but if i use adaptor of 5v/2A, the board is working well.

I assume the mini2440 and any power supplies are at room temperatures.

Has the duty cycle on the PWM hit a maximum value?

Maybe try monitoring the supply current and see if that changes when your
heater goes above 300 degrees.  Then try watching the supply voltage with
an oscilloscope through this temperature range.

Tell us how you interface the PWM output to the heater, SSR, drivers?

pwm works depend on given temperature range, i have set a temperature range
 depends upon that duty cycle varies...

 here i am using a opto, nothing but level transulator, the gpio gives
3.3v, but heater requires 24v, this ic converts 3.3v to 24v with same duty
cycle.