Hi Q,
The 90's LED's where not super bright, usually required about 20mA for a decent brightness.
E

BTW: the number '8' will have all 7 segs lit, 7*20mA= 140mA, thats three times the abs value for the 4543.!!!

Hi all,
Am i reading the data sheet wrong?
Here is the one I am using http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS005128.PDF
In the section marked Absolute Maximum Ratings, the sheet lists:
DC Output Current, per pin (Iout) +/-25 mA
DC Vcc or GND Current, per pin (Icc) +/-50 mA
Power Dissipation (PD)(Note 3) 600 mW
S.O. Package only 500 mW
--------------
The way that I read this is in a sourcing mode, or common cathode 7 seg LED, each segment could be driven at max 25ma.
In a sinking mode common anode, phase pin high, 50ma per segment (pin). Now the total power dissipation is listed as 600mW. Would this be limiting? i know that some power is require from the chip to drive the pin low, but don't know what that is.

This particular display looks very good at 10ma per segment.

 

Am i reading the data sheet wrong?

You're reading the datasheet wrong. No one operates devices at their absolute maximum ratings. The devices aren't guaranteed to survive those conditions. If they did, going just a bit beyond them would be enough to damage them.

I posted the reasonable current capability in post #20.

 

I posted the reasonable current capability in post #20.

Not trying to have an argument with you, but you stated in post #20 - "Only if driving the LEDs with a half mA is acceptable."
One of the reasons I picked this chip is because of several articles on the web. Here is a screen shot of one. Again I appreciate your help.

 

One of the reasons I picked this chip is because of several articles on the web. Here is a screen shot of one.

The referenced material is wrong.

There is a lot of incorrect information on the Web. You can't separate the wheat from the chaff if you won't educate yourself.

 

Buffer the outputs from the HC4543 with a ULN2003

 

Buffer the outputs from the HC4543 with a ULN2003

Or with a TBD62003, the mosfet version.

Bertus

 

I never knew there was a MOSFET version! I suppose I've never needed anything quicker than the good old darlingtons. It's not too pricey, either.
Good idea if it's being multiplexed - stops the ghost images.

 

I'm not here to debate the power capabilities of the HC4543 driver. I wanted to know about the effect of increased voltage to the 7 segment and effect on the chip and circuit.
Looking at other data sheets found this one, https://pe2bz.philpem.me.uk/pdf on typenumber/S/SN74HC4543.pdf
In the data sheet was a equivalent diagram of the inputs and outputs. I added a segment of my LED which now appears to be in the 12volt range, although looks very good at 9V dropped thru 330 Ω, about 10mAI drew my voltages and circuit on to this. It looks like to me if I did this that about 4V above the 5V would leak by the output probably destroying all of the processing chips etc. I know the National Semi MM74HC4543 must be some tough buggers because at one point they had 12V as VCC running thru them for at least 1/2 hour. They were warm. Found out the cheap linear regulator on my bread board shorted to source VCC at 12 V.
Now that I guess I have answered some of my question.
I have to add some transistors...
Would this be correct ? I think the phase input would need to be low (sourcing segment) If this is correct how is a ULN2003 integrated?
Again, thanks for your help.
Rich

 

The UL2003 is just a bunch of transistors, so exactly the same as your circuit above.

 

Thanks, So if I use ULN2003 or TBD6200x, they would go like this? The turn on signal would then be a HIGH output from driver to input? Is there an advantage of one array chip over the other?

 

Yes. Spot on!

 

Is there any preference to the ULN2003 or TBD6200x ?

Since I have to do a redesign, does the 74HC4511 or CD4511BE make a difference?
The pin out is the same..

 

The ULN2003 is a slow old thing. I don't know if your display is multiplexed, but if it is, you'd be better off with the faster MOS version. If it is direct-drive, it won't matter.
For a multiplexed display, you will get ghost images if the drivers don't switch off quickly

 

The ULN2003 is a slow old thing. I don't know if your display is multiplexed, but if it is, you'd be better off with the faster MOS version. If it is direct-drive, it won't matter.
For a multiplexed display, you will get ghost images if the drivers don't switch off quickly

No multiplex. Keeping it simple to 8 data lines. 4 BCD, with 4 Latch select lines. Like a 74HC4511 for the decoder.