🚀 go-pugleaf

In article <1992Nov21.024740.19971@csusac.csus.edu>, chenh@neptune.ecs.csus.edu (H. Philip Chen) writes:
|> rky57514@uxa.cso.uiuc.edu (Tall Cool One ) writes:
|> : Does anyone know about the CD4515 4-bit latched/4-16 line decoder?  I have one
|> : connected to a 4-bit binary counter.  The idea is a sequencer or chaser light.
|> : Problem is that the LEDs light correctly sometimes, and other times, not at
|> : all.  I have the data sheets, and it doesn't tell me anything useful.  I just
|> : want to use th 4514 as a decoder.  I really don't need the latch part of it..
|> : Any suggestions would be greatly appreciated!  Thanks!
|> 
|> Well, I don't claim to know the CD4514/5 that well, but since you 
|> have the datasheets handy, check the max output current of each pin.
|> (I suspect it's not high enough to drive each the LEDs and if so,
|> you'll need to add some line drivers in there.)  Good luck.
|> 
|> 
|> -phil


For driving LEDs, usually the 74C/HC series is better than 4000 series CMOS. The
pin drivers are rated for more current.

The 4515B can source a maximum of 2.4mA when driven from a 15V rail. This reduces
to 0.9mA at 10V and 0.36mA at 5V.

The 74C154 4-16 decoder (unlatched) can drive 8mA at 10V and 1.75mA at 5V.

The 74HC154 can drive a maximum of 25mA per pin (provided total current to chip
<50mA - easy with a one-of-sixteen decoder) at 5V.

JohnH

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