Hi,
Good Day. Can you tell me whether the old component from Motorola MC8601 can be replaced by the 74LS122 without changing the RC element? Thank you very much.
Best Regards,
Ray Vincent
I don't see a full pinout for the motorola part - details on pins 5, 9, 10, and 12 are missing. If we assume they have the same funcitonality (or no internal connection) as the LS122, then it appears that the two are pin-to-pin compatible, at least from a functional perspective.
The two images above come from the TI datasheet (first image) and Motorola datasheet (second image). Here you can directly compare output pulse widths for different RC combinations.
For example, with a 10k resistor and 100pF capacitor, the expected pulse width for the motorola device is ~250 ns, while the TI device shows ~450 ns.
Just given this information, I would expect to have to change the RC components if the devices were switched -- unless the system didn't rely heavily on the precision of that output pulse width.
Hi Emrys,
Good Day. Please see below the response of our customer to you reply. Thank you very much.
for 74LS122 is probably set up differently. but standard 74122 has the same formula as MC8601. please see the picture
in the 8601.pdf are the technical data of a SN29601 manufactured by TI, the part has the same technical data as the 74122, see e.g. t_w (Width of Q output pulse)
Best Regards,
Ray Vincent
Hi Emrys,
Good Day. Please see below the response of our customer to your reply. Thank you very much.
I have to replace the old MC8601 that are no longer in production. Please take a look at an excerpt from the circuit. The first MC8601, Z28 is used without a timing cap, very interesting. The second MC8601, Z29 uses a 5µF capacitor and a 27k resistor. I don't have any information about pulse duration and I don't have an MC8601 to try it out.
Best Regards,
Ray Vincent
