Oh, now I understand your question.
Yes, the maximum voltage at VIN also applies to a lower voltage at VS, i.e. also in your example of VIN=5V and VS=4V.
Please note that although a maximum voltage of 5.5V may be applied to VIN, the recommended voltage is between 0...5V.
Please also note that the logic IOs are not fully TTL compatible: VIH with 1.6V is within the TTL level of 2.4V, but VIL with max 0.6V is slightly out of tolerance (TTL can have 0.8V). Depending on the microcontroller driving the STSPIN240, you may need to provide level shifters.
Good luck!
/Peter
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