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I am reversing a board which some of its IC labels are erased by the manufacturer. I've drowned its schematic in the picture below. The label-removed ICs in the schematic are IC5, IC8, and IC13 which are marked in the picture. The table of resistor values is attached and all of the electrolyte capacitors are 10uF 50V except C9, C10. I have also attached the pictures of the ICs on the board.

The board connects to a motherboard by a 3*32 pin connector which is shown by a rectangle sign with its number in the schematic. I found a text about this board that says the board's job is analog processing of values measured by other motherboard's cards.

From the schematic, I guess that IC13 is a kind of switch-mode power supply and IC5 is maybe a quad digital to analog converter. I searched in datasheets but still, I couldn't find any IC with input and output pins accorded to the schematic.

I hope you can help me to identify the marking code or the family of unknown ICs (IC5, IC8, IC13).

enter image description here enter image description here enter image description here enter image description here enter image description here

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  • \$\begingroup\$ Please let me know if any further information was needed. \$\endgroup\$ – pooya Jul 21 at 9:57
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    \$\begingroup\$ I probably won't be able to answer your question, but I'm sure it would be helpful if you'd describe what this board is supposed to do. And if there are wires going in and out of the board, what those wires are doing and where they are connected in the schematic. Maybe also post a picture of the whole board and possibly the device it came from. Use the EDIT button to add this information to your original question. \$\endgroup\$ – MartinF Jul 21 at 11:04
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    \$\begingroup\$ Perhaps better on the Reverse Engineering Stack \$\endgroup\$ – Solar Mike Jul 21 at 11:09
  • \$\begingroup\$ it's usually written on the die \$\endgroup\$ – Jasen Jul 21 at 19:54
  • \$\begingroup\$ Hard to identify chips without some concept of function of board. \$\endgroup\$ – StainlessSteelRat Jul 21 at 21:45
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My guesses are:-

IC13 - RC4194 Dual tracking Linear voltage regulators

enter image description here

IC5 - AD7549 Dual 12 bit uP compatible DAC

enter image description here

IC8 - LTC1068 Clock-Tunable Quad Second Order Filter Building Block

enter image description here

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  • \$\begingroup\$ Thank you so much! I will test These ICs on the board and tell the final result. \$\endgroup\$ – pooya Jul 23 at 11:53
  • \$\begingroup\$ I found 3 more ICs which have a similar pinout to LTC1068. for IC8. They are LTC1064, LTC1164, and LTC1264. Do you have any idea that which one of them is more probable to be IC8? \$\endgroup\$ – pooya Jul 28 at 13:30
  • \$\begingroup\$ Pin 17 is tied V-, which I think rules out the LTC1264 and LTC1268 because they have fixed Clock-to-Center Frequency Ratios. On the LTC1064 and LTC1164 pin 17 tied to V- selects 100:1 ratio. The LTC1164 has lower supply current than the LTC1064, so that is one way you be might able to tell them apart. \$\endgroup\$ – Bruce Abbott Jul 28 at 18:29

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