Given that it’s an integrated ultra low power SRAM, real-time clock, power-fail control circuit, and battery all in one, I believe you are going to need the help of the heat-pump manufacturer to select a safe replacement.
There are plenty of $20.00 to $50.00 modules with similar functionality still being manufactured, but they have many pinout variations and many incompatible electrical requirements. Choosing the wrong one and trying it could do further damage to the controller.
A fair price from the manufacturer for a replacement module like this would be $50.00 to $100.00 US plus shipping and handling.
Many thanks for the answer :-). That are not really good news that the component is obsulete. Only for understanding. The battery is only for the internal clock? All other (memory functionality) work further fine without battery power? My problem is that the heat pump manufacturer not further exist
The good thing is that the component is plugged in a socket and I did found in the internet really a replacement :-). But a few printed letters on the component are other (vertical on right side: ‘W0836X’ vs. ‘W2010X’ and under ‘CONTAIN LITHIUM CELL’ is at my actual component written:’ 992M5 VH MYS 99 611 D’ but at the replacment component: ‘990TA VH MYS 99 1128 A’ ). Is perhaps the type of integrated battery but all ‘electical properties’ are the same and Ican use the following component as replacement?
When a product X is obsulete bring then out/exist then from the manufructurer normally a compatible component? If yes document this the manufracturer what is the new compatible replacement if a component is labled as obsulete? Or in other words exist for the M48T59Y-70PC1 in the present time perhaps a ‘newer component’ which is compatible to the ‘older component’ (therefore any newer compatible component can be perhaps used for replacement? When yes which?)
There is no general rule, sometimes there is a substitute, sometimes there is no substitute.
For complex special purpose modules like this one, it is common that there is no substitute. A large amount of circuit engineering at manufacturers is re-designing products because one of the original parts is no longer available.
The person asking can only plug in a part in to an exiting heat pump controller PCB, so I’m pretty sure those won’t work for them. If your certian they are drop-in replacements, then you should update the obsolete part’s web page to show those as direct drop-in replacements.