Led Driver selection help / advice

[dacflyer]

I Built a ring clock many years ago, it used only 4017 chips, kept great time..it sampled it's time base from the 60HZ line power.
The clock has 216 leds.
3 leds x 12 - Red
2 rows of 60 leds ( Blue ) for the minutes and
1 row of 60 ( green ) for the seconds

the only thing i do not like about the clock is having to set it everytime the power blanks out.
So now, i am wanting to upgrade it to a Wifi or GPS , Like the rest of my other clocks.
But what i need help with is a led driver. I've used the TPIC6B595 and the smaller version 596 driver on other projects. but it's limited to 8 outputs.
I did also see something about the TLC592x chip.. It seems to be like a dual TPIC6B595. I think.
I've looked at the MAX7219 driver, its capable of driving 64 leds, but it's a matrix driver. so it basically strobes up to 8 leds.. but i am sensitive to hi speed strobing things ( modern car led tail lights are bad for this effect ).
So i am looking to see if anyone here had any better ideas for a driver.

[haklesup]

The TPIC6B595 is a shift register with Open Drain outputs, Did I find the right one? Why don't you just cascade several of them to get enough outputs. Maybe you can find a CMOS output shift register with enough power to drive the LED without the open drain. A 74ACT family chip should be able to light most LED but can also drive a buffer if you want more current or to use a current source instead of a voltage source for the LED array for better stability. I don't think you need an LED driver chip necessarily if you are willing to tinker with the buffer circuit between the digital chips and the LED, even for high.

Not sure how you intend to reset after power up since in this type of clock the time is just Count in the shift register and not a digital Byte in a regular register. If you want this kind of set-ability and display type, might as well drive the whole thing from the uController outputs, in which case you need a chip with more I/O pins but a familiar core to you.

[dacflyer]

I'm trying to save space,, trying to use a chip that'll power as many leds in a single chip..I'd need over 18 chips for the TPIC6B595's that's over kill, and no room,,

[haklesup]

Scanning Digikey, the vast majority of shift registers are 8bits, some in small packages, but Microchip has some interesting 64 bit chips with Voltage level shifting that you might be able to make use of. Here is one, others are in the same product family with varying bits and output max voltage I saw one up to 96 bits
http://ww1.microchip.com/downloads/en/D ... 05877A.pdf (8 to 80V output)

a 16 bit (for hrs) and two 64 bit shift registers (for Min, Sec) ought to do it
https://www.digikey.com/product-detail/ ... ND/4902492
https://www.digikey.com/product-detail/ ... ND/4902507

Not sure if 3 PQFP still has less floor space than 16x SOIC-16 or TSSOP-16 or one of the QFN packages, that still may use less floor space on a PCB and may result in fewer layers because you can distribute the chips near the LEDs they power, the QFP will result in routing bottlenecks causing you to increase PCB layers.

Nice thing about the outputs on this, they are powered separate from the chip logic so you could turn off the display or have brightness settings if you wanted. With a little higher output voltage, you will need to scale the LED dropping resistor, maybe you you could slip an LED current source supply in place of VPP as long as it stayed inside the V range of the chip during operation (max no load V less than VPPmax).

As for the strategy for resetting from GPS formatted data, I am not sure. you would need to convert the time into seconds since 12:00 and then burst that many pulses onto the clock line until the proper time is displayed. Could be interesting to watch.