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'[EE] Looking for recommendation: high-side LED dis'
2019\02\26@141933 by Dwayne Reid

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Good day to all

Several years ago, we purchased the assets of a LED clock manufacturer in our town.  We wound up with several hundred 4-digit red LED displays used for clocks installed in schools and hospitals.  Part number SK-2545D-24

Nice displays: digits are about 2-3/8" tall and decently-bright.  That's the good.  The bad is that these are direct-drive displays: no multiplexing **AND** they are common-cathode.  This last really sucks.

These are RED displays.  Each segment has 3- red LEDs in series, the other dots are all single LED, including two individual LEDs for the colon.

So: I'm looking for recommendations for a high-side LED display driver chip.  I need something like 35 channels, preferably with constant-current output.  The segments having three LEDs means that the driver needs to operate from at least 10 Vdc, preferably 12 Vdc.  Assume around 20mA or less per LED or LED group.  Serial SPI preferred but would accept I2C if that was the only option.

Idea is to make a driver board for these displays that also holds a PIC and power supply.  We can then either use these displays / driver board for our own projects or flog them to willing buyers.

I'd ask on electronics.stackexchange.com but product recommendations are specifically prohibited on that site.

Any suggestions greatly appreciated.

Many thanks!

dwayne

-- Dwayne Reid   <spam_OUTdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
780-489-3199 voice   780-487-6397 fax   888-489-3199 Toll Free
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2019\02\26@150346 by Denny Esterline

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I've not touched one, but I was reading the datasheet for an ST L99CL01XP
last week.
www.st.com/resource/en/datasheet/l99cl01xp.pdf
8 channel, high side, SPI and direct control, automotive voltage range.

-Denny


On Tue, Feb 26, 2019 at 12:20 PM Dwayne Reid <.....dwaynerKILLspamspam@spam@planet.eon.net> wrote:

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2019\02\26@170733 by Dwayne Reid

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Hi there, Denny.

I haven't looked at this part previously.  But: it seems like massive overkill for my application **plus** does not have constant-current output.  But I'll check pricing and see if it makes sense, even if I have to add external current-limit resistors.

I greatly appreciate the suggestion and hope that there are other suggestions coming.

Many thanks!

dwayne


At 01:03 PM 2/26/2019, Denny Esterline wrote:
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-- Dwayne Reid   <dwaynerspamspam_OUTplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
780-489-3199 voice   780-487-6397 fax   888-489-3199 Toll Free
http://www.trinity-electronics.com
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2019\02\26@173601 by Brent Brown

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The TLC5940 may be worth looking at. 16-Channel LED Driver With DOT Correction and Grayscale PWM Control. Serial data interface (which I guess is SPI like). I've designed them into a PCB before on a customers request, but I didn't have to do the programming.

http://www.ti.com/lit/ds/symlink/tlc5940.pdf

On 26 Feb 2019 at 12:19, Dwayne Reid wrote:

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2019\02\26@180114 by stephen.forrestn/a

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What did the clock maker use? No stock of those?

Stephen

> -----Original Message-----
> From: KILLspampiclist-bouncesKILLspamspammit.edu <RemoveMEpiclist-bouncesTakeThisOuTspammit.edu> On Behalf Of
> Brent Brown
> Sent: Wednesday, 27 February 2019 9:36 AM
> To: Microcontroller discussion list - Public. <spamBeGonepiclistspamBeGonespammit.edu>
> Subject: Re: [EE] Looking for recommendation: high-side LED display driver
>
> The TLC5940 may be worth looking at. 16-Channel LED Driver With DOT
....
> http://www.ti.com/lit/ds/symlink/tlc5940.pdf
>
Except:

> On 26 Feb 2019 at 12:19, Dwayne Reid wrote:
....
> > multiplexing **AND** they are common-cathode.  This last really sucks.
> >


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2019\02\26@194814 by Dwayne Reid

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Hi there, Brent.

Unfortunately, this appears to be a sinking driver rather than sourcing.  But that does remind me to check what other devices that TI might have available.

Many thanks!

dwayne


At 03:35 PM 2/26/2019, Brent Brown wrote:
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-- Dwayne Reid   <TakeThisOuTdwaynerEraseMEspamspam_OUTplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
780-489-3199 voice   780-487-6397 fax   888-489-3199 Toll Free
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

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2019\02\26@202922 by Spehro Pefhany

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Hi Dwayne:-

More of a minimum BOM cost than a minimum parts count idea, but I would consider 74HC595 (5) + ULN2003A (5) (or the 8-channel version) + dual PNP prebiased transistors (18)  total 28 cheap jellybean parts.

Best regards, Spehro Pefhany
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2019\02\26@214314 by enkitec

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    MAX7219 perhaps?

    There is a circuit for use with 2,3" displays in the datasheet.

    Mark Jordan


On 26-Feb-19 21:48, Dwayne Reid wrote:
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2019\02\27@055240 by AB Pearce - UKRI STFC

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Hmm, bit of an odd beast, only information I could find on the web was this ...
https://4donline.ihs.com/images/VipMasterIC/IC/RGAC/RGACD005/RGACD005-108.pdf?hkey=EF798316E3902B6ED9A73243A3159BB0

I would be tempted to use a TPIC6A595 shift register from TI which has 50V capable outputs and then either an array of emitter followers or PNP transistors to drive the individual segments.

The single diodes like the AM/PM/colon could probably be driven by transistors driven directly from the PIC.



{Original Message removed}

2019\02\27@105544 by speff

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Quoting Dwayne Reid <EraseMEdwaynerspamplanet.eon.net>:

> Good day to all
>
> Several years ago, we purchased the assets of a L

By the way, if you create negative supply (perhaps with a
inverting boost converter) you could use a 74HC595 chain to
switch the anodes directly (just resistor networks in series).

I did something similar to this with a common anode display
some years ago, and  deliberately gave the power supply a
temperature coefficient to match the LED tempco.

--Spehro Pefhany



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2019\02\27@122537 by Dwayne Reid

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Hi there, Spehro.

I was actually heading down that path myself: having a chain of 4- HC595 shift registers with their ground pin shifted by about plus 3 Vdc and using simple level-shift circuit on the control and data lines.  The single-LED dots would use another HC595 that wasn't ground-shifted.

The advantages of doing it this way are: single-dot HC595 is at the PIC ground potential **and** there is minimal ground current on the level-shifted HC595 chain.  So the level-shifted power supply ground might just be a single LED with appropriate bias resistor (to keep the LED lit).  Have to work the numbers but seems reasonable at first blush..

I'm going to have to look hard at the package dissipation and maximum package current ratings for the HC595 - 28- segments split over four packages is 7 segments per package at 20 mA per segment for a total of about 140 mA current per package.  That seems too high at first glance but the data sheet should tell all.

Many thanks!

dwayne


At 08:54 AM 2/27/2019, RemoveMEspeffEraseMEspamEraseMEinterlog.com wrote:
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-- Dwayne Reid   <RemoveMEdwaynerTakeThisOuTspamspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
780-489-3199 voice   780-487-6397 fax   888-489-3199 Toll Free
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

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2019\02\27@165029 by stephen.forrestn/a

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4511 CMOS with Vdd = 12 V & level shifters on the BCD I/P?

Also, if only 12 hr clock, the MSD (hour  10's) can be treated as a single LED string with the two segments paralleled. So you only need three 7-segment drivers. Add another single LED to indicate AM/PM if needed.

Stephen

> {Original Message removed}


'[EE] Looking for recommendation: high-side LED dis'
2019\03\06@112855 by Mr Smiley
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TM1638

:0)
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2019\03\06@152954 by Bob Blick

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OP needs to drive three LED in series strings. I don't think TM1638 work above 5V. The price is right though.
Cheerful regards, Bob
________________________________________
From: EraseMEpiclist-bouncesspamspamspamBeGonemit.edu <RemoveMEpiclist-bouncesKILLspamspammit.edu> on behalf of Mr Smiley <mr_smiley_homeSTOPspamspamspam_OUTyahoo.com>
Sent: Wednesday, March 6, 2019 11:28 AM
To: spamBeGonepiclistSTOPspamspamEraseMEmit.edu
Subject: Re: [EE] Looking for recommendation: high-side LED display driver

TM1638

:0)
--

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2019\03\06@185011 by Dwayne Reid

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Hi there, Bob.

I'm glad that you commented on Mr Smiley's message - I did not receive that message.

But you nailed it when you suggested that it won't work.  Not only does each segment have three LEDs in series, but the display is direct-drive (no multiplexing).  The display connector has 37 connections.

That said - I wasn't aware of the TM1638.  I'll keep it in mind for other projects.

I have considered using 4- 74HC595 shift-register chips as a high-side driver by shifting the ground pin by 3.5 Vdc or so, then using simple level-shift circuits for the data, clock, strobe pins.  But the maximum package current for the HC595 is 70mA and I want to drive the segments at 20mA each (140mA total per package).

I also considered using the CD4511 decoder/driver chips that the original manufacturer used.  Downside with those is that I truly do NOT like the "6" and "9" digits from the 4511 (top / bottom bar is missing) **and** I can't send arbitrary segment patterns to the display (HELP, OUCH, On, on, oFF, OFF, etc).  You get the picture.

Sephro suggested just adding a whack of jellybean dual PNP transistors - that is still an option.

So - I'm still looking for suggestions.  This doesn't need to be done now but we've been sitting on these displays for quite a while now and it would be nice to make use of them.

Many thanks!

dwayne


At 01:29 PM 3/6/2019, Bob Blick wrote:
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-- Dwayne Reid   <.....dwaynerspam_OUTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
780-489-3199 voice   780-487-6397 fax   888-489-3199 Toll Free
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

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2019\03\06@201324 by stephen.forrestn/a

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HEF40244?
Would need a level shifter as well. Limiting parameter will be Idd(max) so maybe need more than one per digit. Seems to be an active part.

Stephen


> {Original Message removed}

2019\03\06@203243 by Brent Brown

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Doh, my bad on the sidedness.

My favourite high side device is the VN340. https://www.st.com/en/power-management/vn340sp-e.html

Four channels, 0.7A or 1A per channel depending where you read. Overkill, but easy to use. See VN330, VNQ660 & VNQ690 for other currents. Not current regulating, just temp and overload protected etc, so would need resistors.. Reverse supply protection added by a small signal diode, see notes in 660/690 data-sheet. Don't buy from Ali-Express (bought 30 to try them out... no function whatsoever, no refund whatsoever).

If you could mux the 4 x digits with your proposed driver board you'd only need 2 x VN340s to drive the 7 segments, plus a discrete NPN or N-channel transistor for low side switching each digit. The 2 x LED's for the colon could perhaps be driven directly from the 8th channel and GND if decimal points not required, or treat the colon as a 5th digit and mux with the rest, or perhaps hard-wire the colon on all the time.

The VN340 has significant switching delays... but a mux rate of some hundreds of Hz or perhaps a few kHz should be achievable/acceptable.

Brent.

On 26 Feb 2019 at 17:48, Dwayne Reid wrote:

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2019\03\07@010044 by Mark Rages

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On Wed, Mar 6, 2019 at 4:53 PM Dwayne Reid <TakeThisOuTdwaynerKILLspamspamspamplanet.eon.net> wrote:
> I have considered using 4- 74HC595 shift-register chips as a
> high-side driver by shifting the ground pin by 3.5 Vdc or so, then
> using simple level-shift circuits for the data, clock, strobe
> pins.  But the maximum package current for the HC595 is 70mA and I
> want to drive the segments at 20mA each (140mA total per package).

The output of a 74HC595 won't go below it's ground pin.  Are you sure
this would turn off the LEDs sufficiently?

I suggest: bias all the LEDs "on" with resistors to the desired
current.  Then use the open-drain xPIC6C595 (where x varies per
manufacturer) to short out the unwanted segments.

-- Regards,
Mark
markrages@gmail
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2019\03\07@223633 by Jerson Fernandes

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Will the UDN2981 help you? 
Recommended for high-side switching applications that benefit fromseparate logic and load grounds, these devices encompass load supplyvoltages to 50 V and output currents to -500 mA. These 8-channel sourcedrivers are useful for interfacing between low-level logic and high-currentloads. Typical loads include relays, solenoids, lamps, stepper and/or servomotors, print hammers, and LEDs.

Regards
Jerson Fernandes 

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2019\03\08@042400 by AB Pearce - UKRI STFC

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Looks like Microchip supply a version of this part ...

https://www.microchip.com/wwwproducts/en/MIC2981



{Original Message removed}

2019\03\08@193848 by Dwayne Reid

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Good day, Alan & Jerson.

I actually have several rails of DIP versions of ULN2981 sitting on the shelf.  Downside is that they are parallel-in devices, and thus need to be driven by something like a shift register.

Thanks for the suggestions, and please keep more coming.

Many thanks!

dwayne


At 02:23 AM 3/8/2019, AB Pearce - UKRI STFC wrote:
>Content-Transfer-Encoding: base64Looks like Microchip supply a
>version of this part ...
>
>https://www.microchip.com/wwwproducts/en/MIC2981
>
>
>
>{Original Message removed}

2019\03\09@170755 by AB Pearce - UKRI STFC

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But the serial in parallel out could be a single PIC with lots of pins and a tiny bit of software to take SPI (or I2C) in and stick it out parallel ports.



{Original Message removed}

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