Simple "LED driver" chip?
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From: Richard H. on 6 Apr 2006 10:47 I'm looking for a driver chip to run several "high-current" (20-30mA) LEDs from a single MCU. I've got enough MCU pins for a 1:1 solution, but the current exceeds the MCU ratings for direct connection. There's no shortage of advertisements for LED driver chips like Maxim's MAX6966, which could do the job (via SPI). I've got to think there's a simple multi-channel transistor package for this purpose, but Digikey searches on "buffer" or "driver" turn up too many hits to filter through. What generic part number should I be searching for (and how does one find these generic numbers in the first place)? Also, is there any trick to driving blue & white LEDs, or just additional current and higher forward voltage? Thanks, Richard
From: martin griffith on 6 Apr 2006 10:56 On Thu, 06 Apr 2006 07:47:28 -0700, in comp.arch.embedded "Richard H." <rh86(a)no.spam> wrote: >I'm looking for a driver chip to run several "high-current" (20-30mA) >LEDs from a single MCU. I've got enough MCU pins for a 1:1 solution, >but the current exceeds the MCU ratings for direct connection. > >There's no shortage of advertisements for LED driver chips like Maxim's >MAX6966, which could do the job (via SPI). I've got to think there's a >simple multi-channel transistor package for this purpose, but Digikey >searches on "buffer" or "driver" turn up too many hits to filter through. > >What generic part number should I be searching for (and how does one >find these generic numbers in the first place)? > >Also, is there any trick to driving blue & white LEDs, or just >additional current and higher forward voltage? > >Thanks, >Richard uln2803 martin
From: Steve at fivetrees on 6 Apr 2006 10:57 "Richard H." <rh86(a)no.spam> wrote in message news:IR9Zf.12763$kT4.6195(a)fed1read02... > I'm looking for a driver chip to run several "high-current" (20-30mA) LEDs > from a single MCU. I've got enough MCU pins for a 1:1 solution, but the > current exceeds the MCU ratings for direct connection. > > There's no shortage of advertisements for LED driver chips like Maxim's > MAX6966, which could do the job (via SPI). I've got to think there's a > simple multi-channel transistor package for this purpose, but Digikey > searches on "buffer" or "driver" turn up too many hits to filter through. Devices like the ULN2803/4 spring to mind... perhaps a bit old in the tooth these days. Steve http://www.fivetrees.com
From: Spehro Pefhany on 6 Apr 2006 11:55 On Thu, 06 Apr 2006 07:47:28 -0700, the renowned "Richard H." <rh86(a)no.spam> wrote: >I'm looking for a driver chip to run several "high-current" (20-30mA) >LEDs from a single MCU. I've got enough MCU pins for a 1:1 solution, >but the current exceeds the MCU ratings for direct connection. > >There's no shortage of advertisements for LED driver chips like Maxim's >MAX6966, which could do the job (via SPI). I've got to think there's a >simple multi-channel transistor package for this purpose, but Digikey >searches on "buffer" or "driver" turn up too many hits to filter through. If it's several, as in 2 or 3, just use transistors, BJT or MOSFET. Darlington arrays as others have suggested would be better if you have more than four... keep in mind that they have significant foward drop on a 3-5V circuit (which may be a factor if you're using blue or white LEDs). You might also be able to use a HCMOS shift register. >What generic part number should I be searching for (and how does one >find these generic numbers in the first place)? There are hundreds of possible solutions. >Also, is there any trick to driving blue & white LEDs, or just >additional current and higher forward voltage? > >Thanks, >Richard Pretty much. If you're running small LEDs at that high a current you may well have reliability and lifetime problems, particularly when the ambient temperature gets high. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
From: Ryan Weihl on 6 Apr 2006 12:14
Richard H. wrote: > I'm looking for a driver chip to run several "high-current" (20-30mA) > LEDs from a single MCU. I've got enough MCU pins for a 1:1 solution, > but the current exceeds the MCU ratings for direct connection. > > There's no shortage of advertisements for LED driver chips like > Maxim's MAX6966, which could do the job (via SPI). I've got to think > there's a simple multi-channel transistor package for this purpose, > but Digikey searches on "buffer" or "driver" turn up too many hits to > filter through. > > What generic part number should I be searching for (and how does one > find these generic numbers in the first place)? > > Also, is there any trick to driving blue & white LEDs, or just > additional current and higher forward voltage? > > Thanks, > Richard you can use a 74HC4094 shift reg to drive 8 led's with 1 ea 470ohm resistor. rw -- |