Cheap XR2206 Function Generator Overheating...

Hi Kas (mobile so please excuse the briefness), it could be the first time it was reversed, and that has now caused the damage. If you get a chance, check out the 'DDS' ones on eBay, some are not bad, although they are generally only sine and square wave. I've purchased one to explore in more detail, I will also try to write something up about it if it turns out to be any good. I don't have the URL but can check when I get home.

shabaz,

Thank you, I was thinking that but I was REALLY hoping there was something I was missing. Unfortunately those ICs can only be found on places like eBay since they are now obsolete. I will ask though, why does it only get hot when I connect the ground connection from the scope. Without the scope connected the IC doesn't get warm at all.

Thanks

Kas

Out of interest, what current is the circuit drawing with the load (O'Scope) connected and not connected?

I may be wide of the mark here but the XR2206P has a minimum supply of 10V (Max 26V) - and a typical current draw of 12mA (Max 20mA)  -  XR22106CPD is 14-20mA.

Possibly driving it with a reduced voltage may cause it to draw more current to meet it's power requirements?

Also, output impedance could possibly be an issue, RH Electronics list a kit with an output impedance of 600 ohms - again, could too low an impedance cause excessive current draw?

(Incidentally, the RH kit has a supply of 12V and between 12-20mA supply current requirements . . . . . . ).

Or I may be talking total cack!

Specs and test cct taken from Sparkfun Website

(I have no affiliation to the websites listed - they just popped up using a 'popular' search engine!!)

If you show us the schematic and exactly where the scope is connected it might be possible to explain the heating up.

A picture might help as well.

MK

the-dubster,

From what I can see it's consuming 0.22A with a supply of 14V. After disconnecting the scope it's still drawing the same current. Maybe it was an illusion that it was only over heating when connected to the scope. (Its also fun doubting yourself after the fact ).

Kas

Hello michaelkellett,

I don't have a good picture of the schematic but I have included one that I have. I should mention as previously mentioned it appears the scope is not having an effect, I just thought it was at the beginning. Doing a second test has shown the IC heating up even with no scope connected.

This is the setup, cart is there just to ensure the two power points don't touch each other.

Here is the schematic, sorry for the really bad quality.

Thanks

Kas

Hi Kas,

If your power supply and scope share a common ground you might short the output of the unit if you hooked the scope probes up in reverse polarity.

John

jw0752  apparently the scope and PSU are not currently grounded - the plug they connect to does not have a ground (old wiring according to kas.lewis

220mA is WAAAAAYYYYY too high @ 14V!  (Absolute maximum rating IIRC is 750mW - 26V @ 20mA is only 520mW - You're ripping 3W plus through that!

Does it still produce the waveforms out?

I suspect you may have a goosed IC . . . .

If it's drawing 220mA then the chip will get hot (3W at 14V makes for a very hot chip) .

Almost certainly the chip is blown.

It's a very long time since I used one of these and I can't remember how easy they were to blow up.

I realise that you want to learn about analogue circuits - do you want to make a signal generator or was playing with it a end in itself. If you want  a signal generator I can make some other suggestions that are not based on obsolete parts and might be more forgiving.

MK

See my last post below - I misread as 22mA and not 220mA - away too high, supply range is 10 (or 14) to 26V - Current is 14-22mA.  That gives a max power dissipation of 520mW - absolute max rating I think was about 750mW. As michaelkellett stated, you're dragging in excess of 3W through this.

That isn't good whichever way you paint it.