Problem of surge currents in PFC's sense resistor (LT1248 & LT1249)

[ocset]

The LT1249 and LT1248 are both CCM PFC controllers. They are very similar chips. 

Why is it that the LT1249 datasheet,  on page 10, recommends a surge current bypass circuit (three diodes)  for the sense resistor , but the LT1248 makes no mention of any need to protect  from  such surge currents?    (eg the rush of current through the sense resistor if the PFC is switched on at Mains peak)
Also, The LT1248 leaves one with a choice of what maximum sense resistor voltage to employ…but what is the maximum? 

LT1249 datasheet:
http://cds.linear.com/docs/en/datasheet/1249fbs.pdf

LT1248 datasheet
http://cds.linear.com/docs/en/datasheet/1248fd.pdf

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[ocset]

Thanks, do you suspect that the LT1248 doesn't need a series diode chain bypassing its sense resistor for those current surges?

[ocset]

Hello,

100A surge on a 0.2R shunt is 20V, 20V over 4k is 5mA. I don't think 5mA is going to kill the chip.

Thanks, the thing is, our sense resistor is 1.2 ohms…so that’s 120V when a 100A surge flow through it.  With the 4k resistor going into the MOUT pin, that’s then 30mA  flowing in the chips ESD diode…that’s a lot.
Do you think we in fact must have  either a zener or a diode chain across the sense resistor?
Why doesn’t the datasheet mention this?

The attached shows the issus...LTspice sim and pdf schem attached.