Looking for Datasheet on old Texas Instruments strobed Digital Clock Chip, M35020

I have a digital clock, (taken from a space heater) which is built around the T.I. M35020 clock chip which has strobed display and buttons...in this application it also takes in basic data from an LM339 from thermistors and outputs data to control relays and TRIACS for the heater...none of which I need to use.

I wish to Re-purpose it as a battery capacity measuring device for Electric Vehicle 7.2v six-cell Ni-MH batteries, where they are discharged into a 1A constant current sink and a comarator "watches" the voltage...as soon as the first cell is flat the c 300mV drop will trip the comparator, disconnect the current sink and stop the clock (but hold the number on the display), which will then read the battery capacity directly.

The clock chip has its own 400KHz ceramic resonator oscillator, but also takes in 50Hz reference from the mains. When the mains is on the 50Hz gates the strobing of the chip and is somehow locked to the 400KHz oscillator, possibly by a P.L.L. inside the chip.

I have fed other frequencies into the 50Hz input, at 10Hz, the display strobes slowly from MSB to LSB of the display and it runs five times slower...as expected. Up to 5KHz it simply strobes faster but works (at norlmal rate) only at some frequencies which presumably lock to the oscillator and at others where lock is not possible it just sort of stops randomly with one seven seg lit up. If the 400KHz oscillator is stopped it can do a multitude of things depending where in the strobing cycle it stopped and how many times the 470nF capacitor I was dabbing between the output side of the resonator and ground "bounced", sometimes it comes back with no change, but the display goes blank when the 400KHz goes, sometimes it latches up, sometomes it comes back with an advanced count.

There are at least four strobed output lines and five strobed input lines with buttons or switches at some intersections, but other intersections are ominously empty and others receive data from the 339 by some clever tomfoolery with pull up resistors to selected strobed output lines...I suspect the "stop watch" function may well lie at one of those unused intersections, but I really need the chip's datasheet for that...AND, for those who thinkGoogle Knows Everything, well not about the M35020 it doesn't!

 

Thanks, it would be appreciated. I chucked most of my data books when I moved house. Kept just NS Linear a Philips HEF4000 Logic and Motorola Linear book. Ironically these seem to be the easiest to find online...but who ever made such a rational decision under the pressures of a house move.

Agreed, there are simpler methods, as you say, but it requires procuring stuff, this stuff, I have right here on the bench.

 

Further Developments, found another digital clock similar, this one has the non-strobed MK50375N clock chip in it, again, Mr. Google seems to have "forgotten" this one too....any success finding those databooks?

 

Problem solved! The The MK50375 is a really logical and simple to use chip. It can drive V.F.D. displays or Seven Segment L.E.D. There is no crystal reference oscillator, phase locked loops or strobing guf. It simply takes the 50Hz (square wave) in on pin 30 via a 1N4148 with the cathode facing out, (so it's some sort of pull-down) . There are a few other pins for "set-the-time" buttons and two programmed timer outputs and that's it!

In this case it is driving a V.F.Display so I thought I needed low voltage A.C. for the heater/cathode, but there is a rectifier for that and it is run off 2.8v D.C. @ c80-100mA, so I was rough as guts and just dropped it from the 12v rail via a 110 Ohm 2W resistor. Bumped up the current consumption from 20mA to around 100mA, but who cares, those batteries contain power to burn anyway.

The BIG PLUS is, when the 50Hz is stopped in the low state, the display freezes...Exactly what I am after! AND, I found two of them, so I can do two batteries at once and get them all done twice as fast.

Test running it from the signal generator demonstrates that it still works with 500Hz in, although it goes a bit silly up near and beyond 1KHz, really funny to see it cranking along with 500Hz in.

I thought I would put this post so others might gain something by reading it and as I noticed not many others seem to post when (or if) their problems are resolved and reach some conclusion of just remain unsolved.

 

Unfortunately I turfed most on my data books when I moved to a smaller house. I had a mate with a big workshop in the basement of the Chemistry Department at the University of Tasmania, he was the last tech standing and had gone from working on N.M.R. machines to fixing photocopiers. He recently retired and most of his workshop was turfed, including two bookcases of data books. There was so much stuff it has been appearing in at the tip shops for months. The University seems to be heading toward being a "paper" university with just more bums-on-seats in front of computers....as a society we must be careful we don't inadvertently "lobotomize" ourselves, and all this movement from libraries to date centres is a step in that direction.