The Venera landers that the USSR sent to Venus in the 1970s and 1980s were able to survive for up to 2 hours by heavy use of refrigeration and pre-cooling.

But now researchers are testing electronics based on silicon carbide, which can work without special protection at very high voltages and temperatures:

The chip, a simple 3-stage oscillator, kept functioning [in Venus-like conditions] at a steady 1.26MHz for 521 hours (21.7) days before the [test rig] had to be shut down.

https://arstechnica.co.uk/gadgets/2017/02/venus-computer-chip/.