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| Using Darlington Tranistors as BJT |
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| thinkfat:
I guess you'll be needing high-side drivers, too, I've used TBD62783 for LED matrix applications with good success. Another suggestion to further reduce BOM items, use a TLC5916 as the low-side sink driver. It's similar to the TPIC6A595, but it works as a constant current sink with a single resistor to set the current. |
| Oleenick:
--- Quote from: thinkfat on October 09, 2019, 11:55:10 am ---I guess you'll be needing high-side drivers, too, I've used TBD62783 for LED matrix applications with good success. Another suggestion to further reduce BOM items, use a TLC5916 as the low-side sink driver. It's similar to the TPIC6A595, but it works as a constant current sink with a single resistor to set the current. --- End quote --- Unless I'm mistaken I don't need high side drivers as I am only connecting and disconnecting the GND of the LEDs using the TPIC6A595 or possibly the TLC5916. The TLC5916 looks very interesting and since I have 64 connections to switch of each colour, I'll be able to use 8 drivers per colour with current settings to match said colour. I'm always astonished to find these magical application specific ICs, is there somewhere like the TI website that makes it easier to find them or is it down to experience? |
| thinkfat:
Well, unfortunately I don't have a recipe here for finding these, the landscape is just too big. It basically boils down to finding the right "enchantment" to search for at mouser or digikey and then using the parametric search to home in. If you want to further reduce BOM count, I think there's also a 16 channel version of the TLC5916. I leave it to you for hunting it down, now that you know the manufacturer and the family, it shouldn't be that hard. Regarding the high-side drivers, I thought you were doing an LED matrix, and those are usually arranged in rows of which only one is enabled at a time. |
| jhpadjustable:
--- Quote from: Oleenick on October 14, 2019, 08:43:00 am ---I'm always astonished to find these magical application specific ICs, is there somewhere like the TI website that makes it easier to find them or is it down to experience? --- End quote --- I have spent many late nights just leafing through some Aliexpress dealer's collection of surplus ICs and searching the web for part numbers and documentation to see if the IC is interesting to me. Sometimes it isn't very interesting at all, just another switching converter or low-rent MCS-51 microcontroller. Sometimes it is just what I need at that moment. And sometimes it's a chip with some very interesting capabilities that I want to file away for later. By this method, several months ago I found the Macroblock MBI5050, a 16-column PWM LED driver with 8 rows of memory. If you can find the "confidential" app note, find a source suited to your quantity needs, and meet its slightly convoluted timing/clocking requirements, it might be just perfect for you. |
| Oleenick:
--- Quote from: thinkfat on October 14, 2019, 09:27:30 am ---Well, unfortunately I don't have a recipe here for finding these, the landscape is just too big. It basically boils down to finding the right "enchantment" to search for at mouser or digikey and then using the parametric search to home in. If you want to further reduce BOM count, I think there's also a 16 channel version of the TLC5916. I leave it to you for hunting it down, now that you know the manufacturer and the family, it shouldn't be that hard. Regarding the high-side drivers, I thought you were doing an LED matrix, and those are usually arranged in rows of which only one is enabled at a time. --- End quote --- --- Quote from: jhpadjustable on October 14, 2019, 04:02:48 pm --- --- Quote from: Oleenick on October 14, 2019, 08:43:00 am ---I'm always astonished to find these magical application specific ICs, is there somewhere like the TI website that makes it easier to find them or is it down to experience? --- End quote --- I have spent many late nights just leafing through some Aliexpress dealer's collection of surplus ICs and searching the web for part numbers and documentation to see if the IC is interesting to me. Sometimes it isn't very interesting at all, just another switching converter or low-rent MCS-51 microcontroller. Sometimes it is just what I need at that moment. And sometimes it's a chip with some very interesting capabilities that I want to file away for later. By this method, several months ago I found the Macroblock MBI5050, a 16-column PWM LED driver with 8 rows of memory. If you can find the "confidential" app note, find a source suited to your quantity needs, and meet its slightly convoluted timing/clocking requirements, it might be just perfect for you. --- End quote --- Thank you all for your help. I'm well on my way to deciding that hardware to use now. For the high side drivers I'll be using 8 IRF9Z34N P-MOSFETs, for the 8 horizontal rows that I will be quickly cycling and then turning on individual LEDs in verticle columns. This will draw MAX currents of 6A so I believe MOSFETs are the way to go, unless you advise otherwise @thinkfat? |
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