Unknown TI Logic IC - Page 1
Forum section: electronics / beginners

author: ironmanisanemic
author_rank: Newbie
timestamp: August 29, 2020, 11:15:26 pm
content: Hello,I have lurked these forums for quite a while, but this is my first time asking the community for help.I am working on a project trying to reverse engineer a Ford engine management computer from the late 80s. Most of the chips appear to be custom, or at least security through obscurity. There has been some leaked documents that cover the inner workings of the custom intel microprocessor, but there isnt much about the circuitry outside of the main microprocessor.Ive made some feeble attempts to search for the markings on the ICs, and have come up with nothing. Some recently surfaced documents have helped me identify some as just standard 74HC logic, but others still seem to be a mystery.One has a Texas Insturments marking, but none of the other markings help identify it. Even the documentation shows no other part numbers for these ICs leading me to believe they are custom. But im hoping the pinout will help someone tell me at least what it could be. One of the noteable pinout oddities is that the middle 4 pins (pins 4,5,12,13) are all ground, but there is only a single VCC pin (specific pin undetermined). I have attached a photo of the IC in question as well as the 2 possible pinouts from the documents I have. The photo is a bit hard to read of the IC because of the conformal coating, but it reads:Code:TI 809 D B903T01Being new to most of this, and being born in the late 80s I dont have the experience with logic ICs that im sure most of you guys have. Any help is appreciated. I am working to understand the circuitry on a relatively simple ECU (low I/O), and work up to more advanced units (higher I/O, transmission controls, Coil on plug, etc...) from the same family, to ultimately create a open source hardware board that would only require a few donor chips, as these ECUs are getting harder to come by for more popular models, but less desireable ECUs are in abundance.Thanks

author: Brumby
author_rank: Unknown
timestamp: August 30, 2020, 12:12:14 am
content: While I'm not familiar with this particular IC, the use of four central ground pins is a common one for chips that will push a little more power than one usually finds in a DIP. These pins are located directly under the die and provide the best thermal path for heat dissipation. In short, they are used for heatsinking.Of the two diagrams, my money would be that this chip is one of the QDD (QuaD Driver?) - but I would be looking for confirming evidence before going with that.Having a circuit diagram would be most helpful, but tracing one out from a board can be quite the challenge...

author: ironmanisanemic
author_rank: Newbie
timestamp: August 30, 2020, 01:52:59 am
content: Thanks for the insite! Didn't realize that the pins themselves could be used for heat dissipation that way. I was leaning towards that specific pinout myself, but haven't made it to that specific part of the board yet to work out the diagram. I am hoping its some somewhat off the shelf IC, but at this point im not holding my breath.But one thing i have been slowly working on is tracing out a full board schematic. I took some high-ish res photos of both sides of the board and have been tracing out the circuits from one known pinout (the main connector) down their respective paths with GIMP (FOSS Photoshop). Keeping each circuit on its own layer makes keeping the clutter and confusion down, and keeps the overlays simple for each circuit. Once i get a complete sketch, i plan on taking that into KiCad and doing up a proper schematic.Quote from: Brumby on August 30, 2020, 12:12:14 am

author: CChin254
author_rank: Regular Contributor
timestamp: August 30, 2020, 05:03:42 pm
content: This may not be a logic IC but can be some sort of motor controller or power IC. It may be helpful to know the components surrounding the chip to make better predictions.

author: ebastler
author_rank: Super Contributor
timestamp: August 30, 2020, 05:34:35 pm
content: I assume you already have this document?http://www.auto-diagnostics.info/pdf/ford_eectch98.pdfSearching the web for "903T01" does not find any datasheets unfortunately, but finds multiple hits from independent distributors which refer to a part designated "71001FB/903T01". And the 71001FB is mentioned in the PDF linked above, although very briefly. So I assume that's an alternate part to look for -- but again, couldn't find any datasheets.This part [https://www.mouser.com/datasheet/2/405/snls365b-286556.pdf] is rumored to be equivalent to the 71001FB. At least it has the same pinout as your "QDD" diagram. (And going by the fact that pins 2 and 7 are connected in your PCB photo of the chip, that pinout seems the much more plausible one than the "PSIC" alternative you had shown.)Edit: Here's another similar (equivalent?) IC:https://www.ti.com/lit/ds/symlink/sn75437a.pdf

author: magic
author_rank: Super Contributor
timestamp: August 31, 2020, 07:15:48 am
content: Pin 2 of IC5 is connected to pin 14 of IC17,18,31

author: ironmanisanemic
author_rank: Newbie
timestamp: September 13, 2020, 01:13:49 am
content: Quote from: ebastler on August 30, 2020, 05:34:35 pmSorry it has taken me so long to respond, but life happened and i got distracted working out the circuit to another unknown IC.Thanks for finding this! I too found the 71001FB PN, but i didnt find any equivalents. All i was finding was to some obscure atmel microprocessor. This definetly is helping in my search to unravel the hardware mysteries.Any ideas on the other IC labeled PSIC? Ive gotten a bit more of the board traced out and i found what looks like this other chip. I have attached my schematic as well as the traced out circuit board photos.Thank you!EDIT:My board photos are to big to upload to the site, so here they are linked from my gdrive.https://drive.google.com/file/d/1A_-1mBI3HOAPq3KtZ59IZZXiKXSQh2rL/view?usp=sharinghttps://drive.google.com/file/d/1D9o41Qjnxh6Rz1epA0i6jETXug88xOlb/view?usp=sharing

author: wwhite
author_rank: Newbie
timestamp: February 08, 2022, 07:17:21 am
content: Glad I found this, I am doing similar work. Hope your progress is good.I have found that the chip in question 71001FB/903T01 is a driver to take the lo/hi from CPU 0-5v, then to the driver input, then the output can be 12V. According to those data sheets, could be 70v.For me, and my 1994 EEC-IV SD48, it is actually missing this chip on board, and ones that have it, one input is connected to a High Speed Output(HSO) on CPU, and the output is connected to pin #34. This means that the hardware for DOL is missing on my board.

author: CaptDon
author_rank: Super Contributor
timestamp: February 08, 2022, 03:06:44 pm
content: Why reverse engineer someone else's flaws. Roll your own from scratch!!! If you just build their box you have done nothing. Do your own design top to bottom. You don't need to understand their design, you just need to understand the engine you want to control. Ford's "Better Idea" probably wasn't better to begin with! It was the cheapest piece of crap the engineers could cobble together that would do the task and self destruct 10 minutes out of warranty. Remember the class action lawsuit against GM when the ECU crippled the engine at 60,000 miles, or the head gaskets that failed at about 65,000 miles? Just do your own from scratch. Look at Ford's output waveforms and do your own design. You can't get the house numbered parts or software/firmware anyhow and by now I would guess some of the parts have gone obsolete 10 years ago.