Why the R_SENSE should not be lower than 820Ohm?
The reason for this limitation is related to the maximum power dissipation allowed inside the circuitry connected between IS and VS pins.
In normal operation (IIS(FAULT), IIS(SAT)) the current is generated by the device and it is limited to the valued specified, therefore the power dissipation can be calculated as follows: P = IIS * (VS - RSENSE*IIS)
In Reverse Battery condition, the current is limited only by RSENSE, therefore P = (VS - 0.7V) * 0.7V / RSENSE
The Reverse Battery condition is a more stringent one, therefore for all applications where this could happen (therefore without a central Reverse Battery protection that would block current flowing during Reverse Battery) RSENSE must be higher than 820Ohm. Otherwise, 400Ohm are sufficient according to our estimations.