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Help with connecting HEF4049

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Njubster

Fri Jan 04 2013, 09:55PM

Registered Member #6857 Joined: Sat Sept 22 2012, 08:25AM
Location: Srbija, Novi Sad
Posts: 40

I searched on the internet and found very little about it, probably because it's a common knowledge in electronics, but I don't know how to connect it's pins. I know how inverters work and stuff, but I don't know what should I do with the unused pins of this exact hex inverter.

I connected it to breadboard, trying to switch on a simple LED with 0V on inverters input, but it wouldn't work, so I guess I'm making a mistake somewhere with connecting the chip.

Pinout

What should I do with remaining pins? Should I connect them to ground or something...?
What are those c.s. pins? Any purpose for them?
Can the same voltage source,(12-15V) be used for Vdd and inverters enable/disable signal?

Please help :)

Ben Solon

Sat Jan 05 2013, 02:26AM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

first of all:

there is NO semiconductor datasheet that can't be found when you search for it*. if you cant find maybe kl358, then use a common manufacturer's prefix instead(ie. lm358). chances are that they make it too.

going through the pins:
1 -Positive supply voltage(max 18v)
2-7 -Inverters 1, 2 and 3
8 -Negative supply voltage(0v in most cases)
9-12 -Inverters 4 and 5
13 -Useless
14-15 -Inverter 6
16 -Useless

once you have the power hooked up, just add your led on the output of any inverter with the appropriate resistance to your supply voltage. hooking the input of that gate up to the supply voltage or ground will set the led low or high respectively. for your purposes you can just leave the rest of the inputs floating, but if you where to use the ic in a circuit where you need the inverter to perform optimally, just pull them high or low, wither works. this just prevents charge from building up and causing the floating gates from jumping all over the place.

its as simple of that.

*actually there are, but those are extremely rare devices that you pull out of some old appliance that uses the cheapest of the cheap parts.

Njubster

Sat Jan 05 2013, 12:02PM

Registered Member #6857 Joined: Sat Sept 22 2012, 08:25AM
Location: Srbija, Novi Sad
Posts: 40

Thank you very much, I know I suck at electronics, but I'm trying cause it's awesome.

LED was just a test to see how it works, I need the inverter cause I'm making uzzors2k's replica of Richie Burnett's class E tesla coil. I'm making a PCB cause perfboards are untidy and ugly, and that chip was the only problem I had when designing the board.

I guess that's a kind of circuit where the chip has to "perform optimally". So I could just ground the other pins for example?

Dr. Slack

Sat Jan 05 2013, 12:03PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

ben123324 wrote ...

for your purposes you can just leave the rest of the inputs floating, but if you where to use the ic in a circuit where you need the inverter to perform optimally, just pull them high or low, wither works. this just prevents charge from building up and causing the floating gates from jumping all over the place.

while you can leave CMOS inputs floating, and often get away with it, it's a really, really good idea to put them to valid logic levels, usually GND or Vcc. Often for convenience, I connect them to the output of the used gate next door.

The main reason for this is that the gate voltage could easily go to the point that the inverter is in linear mode, either by random charge accumulation, or package surface leakage putting a Gohm path from output to input, so the gate self biases. Then the current consumption will rise dramatically, as noise picked up on the input causes the output to switch rapidly. In some families, the increased current consumption could be enough to overheat the chip. That's unlikely with a slow thing like 4049, but if it's in an essentially static application where it could run for a year on a battery, if it gets into this state it could drain the battery in a day. And you would be puzzled as to why.

Always connect CMOS inputs, never leave them floating. It's a habit that's worth getting into. We had a problem at work where a CMOS input was floating (even professional engineers can do it) and it didn't cause a problem during product development. When did it cause a problem? When we started selling them.

Njubster

Sun Jan 06 2013, 11:13AM

Registered Member #6857 Joined: Sat Sept 22 2012, 08:25AM
Location: Srbija, Novi Sad
Posts: 40

So, is this okay, or should I change it somehow?

Dr. Slack

Sun Jan 06 2013, 05:09PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

You should change it. While you do have the inputs of the unused gates connected to a valid voltage

you also have the outputs connected to the same potential

The gates are inverters. With the input at ground, the output will drive high. If the output is also grounded, a large current will flow, heating (possibly over-heating) the chip and draining your battery.

You may have been confused with what I wrote - for convenience I sometimes connect the input of a gate to the output of *another* gate next door, and leave its output unconnected

If you have the space (and the forethought) it's not a bad idea to connect the unused inputs to ground or rail with a resistor each, or at least a short length of track each that's easy to cut. That way, it's easier to press the gate into service for the "thing that you forgot".

Njubster

Sun Jan 06 2013, 06:25PM

Registered Member #6857 Joined: Sat Sept 22 2012, 08:25AM
Location: Srbija, Novi Sad
Posts: 40

For this purpose I'll be needing only 2 out of 6 inverters, not more.

How about this option:

The idea is to bring 0 to unused inputs, and simply connect the outpusts (1s) to positive side. Is this bad?

Or should I connect it your way?

And thanks very much for help!

This (

) is my first kicad project so it's probably bad but heh... better than nail polish.

Dr. Slack

Mon Jan 07 2013, 01:58PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

I don't think it's bad, at least for CMOS (might be bad for other families), but I wouldn't do it. There's never a need to connect outputs to rails.

Why constrain your circuit unnecessarily? You might not be able to think of a use for any more inverters now, but I would wager that any experienced member of this board has always, within weeks of starting to test a board, said "I wish I had the complement of that signal" or something similar.

Shrad

Mon Jan 07 2013, 02:59PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

I'd use jumpers to invert or delay signals, if needed

Njubster

Mon Jan 07 2013, 03:00PM

Registered Member #6857 Joined: Sat Sept 22 2012, 08:25AM
Location: Srbija, Novi Sad
Posts: 40

This is just a replica of existing circuit (

), and it uses only 2 inverters, so I'm pretty sure :P And I want board to be as small as possible.

So, your way than?

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