Help needed finding IC datasheet please

[Ice-9]

I am trying to find out what this chip is. The markings on it are ST logo (st microelectronics) and the IC has EF921 marked on it. I have tried google and The ST micro website but I can't find any info at all.

If it helps identify the chip I can explain what part of the circuit it is in. It is an 8 pin dil and it is used in a circuit with a momentary footswitch which then connects to the clock of a D type flip flop. Two flip flops are connected together to create a 2 bit binary up counter. After trying to trace this out it looked like it could have been a dual op amp but when i tried a 4558 it did not work.

The following pins are connected like this

pin 1
pin 2
pin 3
pin 4 = ground 0v
pin 5
pin 6
pin 7 = to flip flop clock
pin 8 = v+ 3.3v

[pjwhite]

Are those the ONLY connections to the IC?  Power, ground and an output don't add up to much functionality except in sensors and reset generators.

Are there any other markings on the chip?  The EF921 might be a date code or manufacturer's internal part number.

[Ice-9]

Yes the other pins do connect to components, I tried to draw out the circuit as if the pins corresponded to dual opamp and they indeed drew up a schematic which looked correct, maybe there nand gates or something as an op amp replacement didnt work, put the original chip back in and its working. The reason i want to know the chip id is that i want to use this in another pedal.

The only markings on the chip are :-


  393

  ST EF921

Thanks for the reply

[CynicalMan]

xx393 is often a dual low-voltage comparator, that might be it:
www.datasheetcatalog.com/datasheets_pdf/L/M/3/9/LM393D.shtml

[Ice-9]

xx393 is often a dual low-voltage comparator, that might be it:
www.datasheetcatalog.com/datasheets_pdf/L/M/3/9/LM393D.shtml

Thanks , that looks promising. I have looked at the datasheet and I think that may be the right component, i will get one to test .