Searching for 8-digit 5*7 LED matrix display driver

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Hi all,

I am searching for a driver for 6-8 digits of 5x7 LED matrix displays.
All I can find seems to be the 4-digit MAX6952/3 chips. Two of these
would ofcourse work, but that requires a lot of space and they are not
cheap either. I do not really need all the font functionality etc. As
long as I can control each LED seperately, I'm OK. Another option would
be a chip with only the drive transistors and current sources and do
the multiplexing in SW.

Does anybody know of chips that might do the job or manufacturers that
carry these things?

Or does anybody know of 30mm 5x7 displays with integrated drivers? All
I have found are 5mm and 7mm, 4 or 8 digits (and with this option I
need 6 digits). Preferably these displays should be available in red
and blue.


TIA,

--
Stef            (remove caps, dashes and .invalid from e-mail address to reply)

Laugh at your problems; everybody else does.

Re: Searching for 8-digit 5*7 LED matrix display driver
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Maxim makes 8 digit display driver chips. Do a search on  MAX7219 or click
on the link below:

http://www.maxim-ic.com/quick_view2.cfm?qv_pk13%39


Other chips that you may want to consider are: MAX6591, ICM7218, ICM7228,
MAX7221.

Good luck on your search.

Mostafa


Re: Searching for 8-digit 5*7 LED matrix display driver

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Probably the cheapest way would be to use a string of 74HC595s as column drivers
and transistors
(maybe driven from a HC138 if I/O is tight) as row drivers, and use a timer
interrupt task to keep
them refreshed.
If CPU usage or IO is tight, you could use a seperate cheap MCU, e.g. PIC as a
display controller to
do the refresh & character generation  and send it the characters serially. A
PIC16F627 at <$2 could
do it easily.



Re: Searching for 8-digit 5*7 LED matrix display driver
oN 11-Jun-04, Stef said:

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You may want to look here:
http://www.allegromicro.com/ic/leddriver.asp

--
Bill
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Re: Searching for 8-digit 5*7 LED matrix display driver
In comp.arch.embedded,
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(Stef) wrote:
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are available.
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drive the columns
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Yes, this can work. I suppose you would drive this in a 1/5 scan ratio and
limit the peak current to the '595's drive capability?

Downside is that there is no current regulation and especially with blue
LED's (Vfwd ~= 3.5V) this can cause significant differences between LED's.
To solve this I'd like to use current drivers. So rearranging the martrix
a little and using a scan ratio of 1/14 (as does the MAX6952) and a
high(er) peak current I come to this:

       1  MBI5027 16 channel current sink
       2  8 channel high-side driver, or 7 dual P-FET, or 14 singles
       2  optionally '595's if there is not enough I/O to drive the P's
      ---
      3-17 parts

This gives me exactly enough drivers to drive 6 digits and an extra
column of 14 discrete LED's. And the already scanning P-FET's allow
for easy scanning of a keypad.

But this TLC5920 also looks nice, it may decrease the part count to 2.


--
Stef            (remove caps, dashes and .invalid from e-mail address to reply)

"Money is the root of all money."
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Re: Searching for 8-digit 5*7 LED matrix display driver
On Tue, 15 Jun 2004 17:01:05 +0200, the renowned

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(Stef) wrote:
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are available.
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drive the columns
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If you use the DMOS open-drain XX595's then you can drive up to a
couple hundred mA per output depending on version (40mA average per
LED, probably too much). You would probably have to upgrade the
p-channel transistors if you go that high (the total power dissipation
of display + drivers + resistors could be as high as 20~30W.

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Current can be significantly different with no visual effect. I think
you'll find it's perfectly acceptable.

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If your average current requirements are rather modest and don't mind
a fair bit of dissipation in the semiconductors and don't mind using
single-sourced parts then it indeed might be the right solution for
you.

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Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
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Re: Searching for 8-digit 5*7 LED matrix display driver
In comp.arch.embedded,
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Ah, never thought of high current 595's, thanks.

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Do you have any experience with this? I've seen some websites saying
that current is important, but those where of current source
manufacturers. ;-)

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I've now got a qoute of under EUR 1.00 (1000+) for a 16 channel current
sink. This would replace 2 high current 595's and 16 resistors. So costwise
current regulation is not bad. Not even single source looks like a problem,
the Allegro and Macroblock parts are pin compatible. I'll have to compare
them in more detail to see if they are fully drop-in replacements.

For now I think I have enough info to select the best solution, pity the
ideal single-chip solution did not pop up.

Thanks to all who replied.


--
Stef            (remove caps, dashes and .invalid from e-mail address to reply)

I hope you millionaires are having fun!  I just invested half your life
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Re: Searching for 8-digit 5*7 LED matrix display driver
On Wed, 16 Jun 2004 12:22:43 +0200, stef33d@yahooI-N-V-A-L-I-D.com.invalid

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I requested 4 samples of Texas Instruments' TLC5920DL two nights ago,
and I received them this afternoon. I will be playing with them as soon as
the boards are returned from the pcb manufacturer. (They have to be
designed yet !!)

I have nothing but praise for TI's response time.


Re: Searching for 8-digit 5*7 LED matrix display driver
On Wed, 16 Jun 2004 12:22:43 +0200, the renowned

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TI has at least two versions with different drive current capability
(and pinout, unfortunately). Single-sourced, AFAIK, but they have been
around for about a decade.

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Rather similar situations. I don't think it's a problem.

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That sounds reasonable. What part did you get the $1.20-ish quote on?
The TI parts are more like $4 USD in 100's.


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
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Re: Searching for 8-digit 5*7 LED matrix display driver
In comp.arch.embedded,
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This was a qoute for the MBI5027. This was for another project, which I
am not involved in, so I don't know the exact numbers. but it was at least
1000+, maybe 5k.

--
Stef     (remove caps, dashes and .invalid from e-mail address to reply by mail)

Kime's Law for the Reward of Meekness:
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