problems with IC while testing it on a breadboard

[techie]

Finally after almost a month of waiting for it my XR 2206 has arrived.
I went to test it on a breadboard.
I connected everything as on the circuit in figure 11 in the datasheet, with the minor difference that the pot at R1 is 1MΩ instead of 2MΩ.
I pre-setted both pots in the circuit to max values.
I checked all connections with an ohm meter.
I double checked connections on the breadboard and in the diagram in the
figure 11.
I chose a low test voltage (12V) close to the minimum specified in the datasheet.
I hooked the output to the scope over a 1/10 probe.
I placed my finger on the IC (first hand temp control ) and turned on the power supply.
Nothing happened, no sings of life at all (i checked all time basses and amplitudes).
Than i tried to see what happens if i move the pot at R3 (for setting ramp/sine, btw i need sine output).
Nothing happens over the entire range of the pot, still completely dead.
I returned R3 pot to its starting position and tried moving the R1 pot (for freq adjust).
Nothing happens, but when the pot reaches about half of its range (~500kΩ) the IC suddenly gets vary hot, so hot i cant keep my finger on it anymore.
Than immediately turned of the power supply.
I triple checked all the connections on the board and on the diagram. No mistake there, at least none i can see.
But result is always the same, the IC heats up fast and plenty when the pot at R1 reaches about half of its value.

WHAT IS GOING ON ?

P.S.
The IC and the datasheet are from the same company.

 

[SYE]

I've also triple checked circuits before, obvious problems are'nt always obvious though. It does sounds like you've got something wired wrongly though.
Post a photo of your breadboard(In focus, Hi res) and you may get more help.

 

[audioguru]

Use a breadboard for DC circuits.
Use a pcb or stripboard for AC circuits.

The datasheet assumes it is on a small pcb and a supply bypass capacitor is there (1uF to ground at pin 4).

What is the value of the frequency determining capacitor between pin 5 and pin 6?

 

[kchriste]

I connected everything as on the circuit in figure 11 in the datasheet, with the minor difference that the pot at R1 is 1MΩ instead of 2MΩ.

Post a link to this datasheet. There are several on the net. Lets all get on the same page so to speak.
What capacitor value did you place between pins 5 & 6?
What is pin 10 connected to?

 

[techie]

Here is the datasheet:
XR2206 Datasheet pdf - Monolithic Function Generator - Exar

I only have
I placed a 1uF capacitor at pin 4 just like in the datasheet.

Capacitor between pins 5 & 6 is 1uF.

Pin 10 is connected to the ground over an 1uF electrolytic capacitor just like in it's in the diagram.

I know not to trust the eye thats why i checked all the connections with an ohm meter before applying voltage to the circuit.

Could it be that heating up already destroyed the IC ? How to know when its destroyed?
Well it didn't have any output in the first place so i cant tell by that method.
As i said i turned of power as soon as it started to heat up.

Considering breadboards i only have one type available. It is this breadboard only from a different manufacturer. This is not a photo of my breadboard,
it is only a pic i found online so i can show you which breadboard type i'm using.

 

[ericgibbs]

Here is the datasheet:
XR2206 Datasheet pdf - Monolithic Function Generator - Exar

I only have
I placed a 1uF capacitor at pin 4 just like in the datasheet.

Capacitor between pins 5 & 6 is 1uF.

Pin 10 is connected to the ground over an 1uF electrolytic capacitor just like in it's in the diagram.

I know not to trust the eye thats why i checked all the connections with an ohm meter before applying voltage to the circuit.

Could it be that heating up already destroyed the IC ? How to know when its destroyed?
Well it didn't have any output in the first place so i cant tell by that method.
As i said i turned of power as soon as it started to heat up.

Considering breadboards i only have one type available. It is this breadboard only from a different manufacturer. This is not a photo of my breadboard,
it is only a pic i found online so i can show you which breadboard type i'm using.

View attachment 24217

hi,
Fig 11, shows two 5K1 resistors forming a divider chain from +V to 0V
with R3 connected to the junction of the divider.
Also on the divider junction is a polarised capacitor.

Is the capacitor the correct way around.????

What is the measured voltage at the junction of the 5K1 divider.???? Tell us.!

The fact that the ic got too hot to touch dosnt sound good, it may have failed.

BTW: 'strip board' or 'Vero board' is the pcb type that you are using.
Bread boards are often referred to as Project boards,,, the type where the components are pushed into sockets,, not soldered.

 

[techie]

The capacitor is the right way around, i checked all components and connections multiple times.

As for the voltage drop need to wait until monday to measure it, labs closed over weekend. I'm working in a lab because i don't have all the equip at home (primarily stabilized DC voltage sources and a scope).

 

[kchriste]

Capacitor between pins 5 & 6 is 1uF.

Is this a non-polarized cap? The datasheet doesn't appear to specify polarity for some reason. Try a 0.1uF instead if you don't have a non-polarized 1uF cap to see what happens.

 

[techie]

Capacitors between pins 5&6 and on pin 4 are non-polarized.
Capacitors at pins 3 & 10 are polarized.
Thats how i connected it, just like in the datasheet.
For polarized caps i use electrolytic caps and for non-polarized block caps.

 

[kchriste]

I can't think of what the problem could be without more information. A picture of your circuit would help. If you wired it exactly as per the diagram, it should work. Maybe you have a defective IC or other component.
Did you measure the voltage on wiper of R3. What voltage did you measure?

 

[techie]

Voltage between the two 5.1k resistors is 5.6V.

I checked and reconnected everything today, problem is still the same. It just gets heated up without any output.

 

[3v0]

Bad chip are uncommon. It is far more common to hook them up wrong and the overlook the error again and again while checking. It happens to the best of us.

Post a good picture of your circuit.

EDIT: The more sure a person is of his circuit being correct, the greater the chance it is wired wrong.

 

[techie]

Ill try to get a camera to take a picture.

 

[ericgibbs]

Ill try to get a camera to take a picture.

hi,
Post a picture of both sides of your pcb.

 

[mvs sarma]

..........
The more sure a person is of his circuit being correct, the greater the chance it is wired wrong.

Well said, 3v0 !

 

[techie]

I found out what was wrong.
In the datasheet there is a dot on pin 1 and there is a dot on the IC as well. So i thought that was the pin1. Actually that dot isn't the marking for pin 1, i don't know why is it there at all. Pin 1 is the left side of the little half moon dip on the opposite side of the IC. Well i had the IC reversely connected 180 degrees, no wonder it didnt work and only heated. I connected it correctly now but only response i get is a Differentiator response when i turn the pot at pin 3.
I think its fryed due to gnd and vcc pins changing place (pins 4 & 12).
Why is that dot there on the oposite side of the half moon dip?
Now i have to w8 one more month for another IC to arrive. :S

 

[kchriste]

Yup, looks like you fried it.

Now i have to w8 one more month for another IC to arrive. :S

Just in case, order more than one this time.

Why is that dot there on the oposite side of the half moon dip?

The notch on a dip chip is the thing to look for. Ignore the dots.
The pins are clearly marked in the datasheet:

 

[techie]

I learned the hard way.
Yes i already ordered again, but this time i ordered 2 just in case.

 

[Pommie]

I know it's a bummer but don't think of it as a failure, think of it as a valuable lesson. Anyone on here with a modest amount of experience has made that same mistake. It's not IF you make that mistake it's WHEN. You now have that mistake out of the way and won't make it again. Others still have that mistake to make and reading this will not stop them making it as it's only when it costs (time or money) that the lesson is learned.

I think I'm currently at mistake lesson 376 and still don't know how long the list is.

Someone on here has a signature something like "lessons learned are directly proportional to cost". That is just so true. Wait till you trash a $xxx,xxxx machine and you get that stomach churning feeling. Glad I got that one out of the way.

Mike.

 

[draeath]

I believe the dots are used for aligning parts in robotic component placement.