Suggestion Part alternatives for the MAX7219/MAX6954 7-Segment LED Driver

[optoisolated]

I'm working on a project which has 16 7-Segment LED modules (maybe more) and am looking for a suitable driver for it. Usually I'd go for the 7219, but i'd need a fair few of them and they are getting rather pricey.. The 6954 is slightly cheaper but still >25 bucks a piece. I'm wondering if anyone has seen any alternatives for 7-Segment LED drivers which would help me get my BOM cost down? Appreciate any advice or tips anyone has. 

[Mr. Scram]

I don't really understand why those parts are so expensive, to be honest.

[optoisolated]

Me either.. Maxim Tax?

[Mr. Scram]

Me either.. Maxim Tax?

Still, there should be a more sensible party producing something similar. It seems the volume should be there.

[optoisolated]

Parametric search on Digikey isn't proving particularly fruitful either. I mean, I could do it with some I/O Expanders, and some transistors, but seems like a lot of mess for something which should be very common, like you say. Plus I really like the idea of a solution that allows me to offload some work from the microcontroller, and has built in latching and brightness control.

[mariush]

You could just get a regular led driver IC with 16 / 24 / 28 / 32 / 36 / more separate channels and use a tiny micro (8-10 pin pic that's less than 0.5$) to act as an in-between  converting your 16 bytes (or however you want to send the data about segments) into the segments which have to be turned on or not... besides this you'd only need a bunch of cheap mosfets or transistors to enable power to groups of leds at a time (because you'll only have a few digits turned on at any point)

or could just have 3-4 led drivers on the same i2c bus, each with its own address, and have a small micro to send segment data to each, but this way you're getting to around 6$ in driver chips so it's not much saving.

for example  IS31FL3235A has 28 channels and it's <2$ in quantity (1.5$ if you get 100) ... that's enough for 4 digits of 7 segments , so you could use either 4 of these each with it's own i2c address, or just multiplex digits, as you have 4 groups of 4 digits.
Would work great if you have ready made 4 digit 7 segment common anode displays.

[optoisolated]

That's not a bad idea.. I will look into those and see if they will do what I need but cursory glance suggests it should do the job. Cheers  

[Mr. Scram]

You could just get a regular led driver IC with 16 / 24 / 28 / 32 / 36 / more separate channels and use a tiny micro (8-10 pin pic that's less than 0.5$) to act as an in-between  converting your 16 bytes (or however you want to send the data about segments) into the segments which have to be turned on or not... besides this you'd only need a bunch of cheap mosfets or transistors to enable power to groups of leds at a time (because you'll only have a few digits turned on at any point)

or could just have 3-4 led drivers on the same i2c bus, each with its own address, and have a small micro to send segment data to each, but this way you're getting to around 6$ in driver chips so it's not much saving.

for example  IS31FL3235A has 28 channels and it's <2$ in quantity (1.5$ if you get 100) ... that's enough for 4 digits of 7 segments , so you could use either 4 of these each with it's own i2c address, or just multiplex digits, as you have 4 groups of 4 digits.
Would work great if you have ready made 4 digit 7 segment common anode displays.

Cheap and small microcontrollers seem available starting at less than $0.30 for ATtinys, but I don't think those have I2C. Controllers with I2C seem to be a lot more expensive, though I have to say that I just did a quick parametric search. I don't think you want to go down the path of bitbanging for something like this.

[austfox]

What about AS1107. They seem to be around the $12 mark.

[chickenHeadKnob]

This is one part where the fake max7219 from ebay make sense. They do work in my experience, though I bought mine years ago and don't know what the  quality is like these days. Would not use them in a product for sale, hobby only. You could also use 74xx595 shift regs in daisy chain.

[maor]

Hey,
How about using a CPLD plus some drivers?
a lattice part costs maybe 2$ and with some lightweight drivers and a pcb you could probably do it in like 5$

https://www.digikey.com/product-detail/he/lattice-semiconductor-corporation/ICE5LP1K-SG48ITR50/220-2064-1-ND/5358105

might give it a shot...

[mariush]

Depending on the seven segment digits you have (for example if you go with single digit common cathode ones) you could even use a single 1-2$ microcontroller.

For example, a 40pin DIP PIC16(L)F18875 has i2c orspi and up to 36 i/o pins... send data to it through i2c and let it multiplex the digits ... you could use 28 i/o pins to drive up to 4 digits directly from the micro, and 4 other io pins to connect 4 digits at a time to ground (multiplexing the 16 digits). You can use resistor arrays (one per digit) to limit current to each segment easily... you'll want to do that as the micros have some limitations ... for example, the datasheet of the pic I mention ha something like 50mA per pin max and 350mA in total (provided evenly spread across all pins)... so with 28 outputs, you still have 350/28 =  ~12.5 mA ... You should be fine with 10mA per segment, even with 5mA per segment depending on led color you choose.

[Mr. Scram]

Hey,
How about using a CPLD plus some drivers?
a lattice part costs maybe 2$ and with some lightweight drivers and a pcb you could probably do it in like 5$

https://www.digikey.com/product-detail/he/lattice-semiconductor-corporation/ICE5LP1K-SG48ITR50/220-2064-1-ND/5358105

might give it a shot...

They don't tend to be very frugal, so it depends on the application.

[maor]

Hey,
How about using a CPLD plus some drivers?
a lattice part costs maybe 2$ and with some lightweight drivers and a pcb you could probably do it in like 5$

https://www.digikey.com/product-detail/he/lattice-semiconductor-corporation/ICE5LP1K-SG48ITR50/220-2064-1-ND/5358105

might give it a shot...

They don't tend to be very frugal, so it depends on the application.

Well if the part he wants costs about 25$, a design with cpld should be about 8$ including a PCB to adapt it to TH, so why not?

[Mr. Scram]

Well if the part he wants costs about 25$, a design with cpld should be about 8$ including a PCB to adapt it to TH, so why not?

The engineering cost could still make it an expensive part, or the product could have a disappointing battery life because CPLDs aren't frugal. Again, it depends on the application.

[mino-fm]

You could also use 74xx595 shift regs in daisy chain.

Or 40HC94 or 4094 shift registers with (40HC94) or without limiting resistors. https://www.mikrocontroller.net/topic/291503#3103604
Static driving will produce no noise and needs no refresh from µC.

[Old Printer]

Im in USA so my sources are probably not $$ smart, but you might be able to find something similar local to you. My local dealer sells these 8x8 LED programmable displays. His regular price is $3.95 but a few times a year he puts them on sale for $2.95. They have a MAX7219 in a DIP socket so it is easy enough to pop them out and use them in another project. That's the only reason I buy them as just the IC can run $7 - $9 alone.

http://www.mpja.com/8X8-Red-Programmable-LED-Matrix/productinfo/34563+MP

[Mr. Scram]

Im in USA so my sources are probably not $$ smart, but you might be able to find something similar local to you. My local dealer sells these 8x8 LED programmable displays. His regular price is $3.95 but a few times a year he puts them on sale for $2.95. They have a MAX7219 in a DIP socket so it is easy enough to pop them out and use them in another project. That's the only reason I buy them as just the IC can run $7 - $9 alone.

http://www.mpja.com/8X8-Red-Programmable-LED-Matrix/productinfo/34563+MP

I can only assume those are fake or reclaimed ICs.

[Old Printer]

Im in USA so my sources are probably not $$ smart, but you might be able to find something similar local to you. My local dealer sells these 8x8 LED programmable displays. His regular price is $3.95 but a few times a year he puts them on sale for $2.95. They have a MAX7219 in a DIP socket so it is easy enough to pop them out and use them in another project. That's the only reason I buy them as just the IC can run $7 - $9 alone.

http://www.mpja.com/8X8-Red-Programmable-LED-Matrix/productinfo/34563+MP

I can only assume those are fake or reclaimed ICs.

I am sure that is possible, but I have yet to have a dud or failure. This is just for personal hobby use so it's not like putting a product in the field and having to service it. YMMV

[floobydust]

Titan Micro TM1638 10 x 8 seg/digit plus 3x8 keyscan. You can get a board with 8-digit LED displays and pushbuttons for $2.50

Holtek HT16K33 16 seg x 8 com plus 13x3 keyscan.

There is a limit to how many digits you can multiplex with one IC before flicker becomes noticeable to the eye.

[viperidae]

$25 for a max7219? It's $16NZD each at element14. $5.62USD at Digi-Key for 1000.
$5.68 each at Maxim's website

[mariush]

Still 3-4$ more than it should be. Shouldn't cost more than 2$ in 100+ quantity.

[David Hess]

I looked into this problem a couple years ago when I noticed the high and increasing price of Maxim's LED display drivers.

I suggest using cheap microcontrollers as display drivers.  Multiplexing can be used to reduce the number of external drive transistors and this should allow a single chip with 12 outputs to drive four 7-segment displays.  For reliability reasons, I do not suggest driving LEDs directly with the microcontroller outputs unless current is under 4 milliamps and the lower the better.

[Mr. Scram]

I looked into this problem a couple years ago when I noticed the high and increasing price of Maxim's LED display drivers.

I suggest using cheap microcontrollers as display drivers.  Multiplexing can be used to reduce the number of external drive transistors and this should allow a single chip with 12 outputs to drive four 7-segment displays.  For reliability reasons, I do not suggest driving LEDs directly with the microcontroller outputs unless current is under 4 milliamps and the lower the better.

With what kind of specific part would you drive them indirectly?

[David Hess]

With what kind of specific part would you drive them indirectly?

The microcontroller obviously needs enough output pins but I would also look for a part with a UART, USART, SPI, or whatever for serial communications rather than trying to bit-bang a receiver.  Using a UART for the serial link may be advantageous because no clock or chip select is required.

I considered PICs first because I am familiar with them and they are available in easy to prototype 300mil DIP packages up to 28 pins providing plenty of I/Os but AVR could work also.  The price would be competitive with a 74HC595 solution and better if multiplexing is used.