Datasheet

Operation STM809/810/811/812
8/21 Doc ID 9873 Rev 5
2.4 Valid RST output down to V
CC
= 0 V
When V
CC
falls below 1 V, the RST (STM809/811) output no longer sinks current, but
becomes an open circuit. In most systems this is not a problem, as most MCUs do not
operate below 1 V. However, in applications where RST
output must be valid down to 0 V, a
pull-down resistor may be added to hold the RST
output low. This resistor must be large
enough to not load the RST
output, and still be small enough to pull the output to ground. A
100 kΩ resistor is recommended.
Note: The same situation applies for the active-high RST of the STM810/812. A 100 k
Ω pull-up
resistor to V
CC
should be used if RST must remain valid for V
CC
< 1.0 V.