HEF4094BT (smd) output current

[Exo]

The HEF 4094 is a serial shift register. I want to use it to drive some multiplexed 7-segment displays, using only 2 µC lines.

Question is, can the chip deliver enough current to drive leds. And because they are multiplexed, im going to have to feed each led with more current then normal to prevent the display getting dim

Anyone know how much current this chip can deliver per output? Can't find it in the philips datasheet (i've got philips ic's here)

 

[panic mode]

**broken link removed**

 

[Roff]

That datasheet doesn't answer your question. You need to look at **broken link removed**. There, you can see that you won't be able to drive LEDs. Have a look at **broken link removed**, which is the same function but with open drain 20ma LED drivers.

If you want to stick to the 4094, the minimum hardware solution is probably emitter followers (NPN for logic high, PNP for logic low), or some small MOSFETs such as 2N7000 (for logic high). Small PMOSFETs for logic low are available, but harder to find.

 

[ukeee]

You could use a 4049 or 4050 buffer, one is inverting the other isn't but I can't remember which way around they are. They can sink 40mA but I think this depends on the supply voltage.

 

[Exo]

Thanks guys. Guess i have to buffer the ouputs then.