I have an ultrasonic transducer driver I am working on reverse engineering for when I inevitably blow it up, but all of the IC's have their markings scraped off.I figured out 99% of the IC's on the board, but this last one has me stumped.

It is an SOIC8, only pins 2,4,5,6, and 8 are connected to any traces. Pin 2 is 5v in from the Vref pin on a SG3525. Pin 4 is Gnd. Pin 5 &6 go to each side of an unpopulated 2 pin jumper.

Pin 8 is a 5v pk-pk square wave output at 60Hz.

Pin 8 goes to the RT pin on the SG3525 after passing through a 10k resistor, pass the cathode of an electrolytic cap (anode connected to 5v Vref), and then through a 150k resistor where it joins the pots used for frequency control.

In my experience, I have not ran across an IC with this behaviour and pinout.

I will post my schematic later if I am allowed.

 

It seems it will allow me to upload my schematic as a PDF for the part of the circuit in question. U5 is the IC I am trying to identify.

 

It’s possible that U5 is a proprietary IC, manufactured only for the products of the manufacturer. Such ICs often will have no markings.

I assume that the supplied schematic is yours? Correct?

I suspect that the unidentified IC may be proprietary.

 

One thing you could try is viewing the i.c with an ultra violate lamp. I had some I.c's where the numbers had been rubbed off but showed up clearly under uv.

 

One thing you could try is viewing the i.c with an ultra violate lamp. I had some I.c's where the numbers had been rubbed off but showed up clearly under uv.

I’d like to add, a common procedure using an UV light source is to use a highlighter and cover the top. Immediately rub the highlighter off with a soft cloth. The ink remains where there once were makings. Doing this makes any previous markings clearer under UV light.

 

Yes, the schematic is of my creation. Thank you both for the UV and highlighter suggestion. The only thing that would make sense for it to be would be some sort of odd VCO, but there is a lack of supporting passive components and the pin map does not match anything I can find.

 

I have some UV LEDs coming in today so I can hopefully pick up some latent details on the IC.
The more I look at this IC, and how it is implemented in the circuit, the more I am starting to think this is something that was lost in translation when the group that made this unit reverse engineered the driver they stole the design from.

I understand what is trying to be done, but there is just an absolute lack of supporting connections to accomplish what this IC is here for.
Since on the SG3525 Pin 6 RT is the frequency control that is adjusted by resistance to ground, by biasing this resistance with an external voltage one could adjust for frequency drift with the right supporting circuit.