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LT3032- unexpected negative output in start-up with SHDNN=Low


We have unexpected negative output in start-up with SHDNN=Low.

Are there any improvement way?

Rising Negative voltage  after positive voltage(OUTP)=5 is required in the circuit.

I think that ADP7182 is good in this case.

Condition table:

INP 0 to 18V in 3ms
INN 0 to -18V in 3ms
OUTP 16V setting
OUTN -11V setting
SHDNP_bar Hi = INP
SHDNN_bar Low= GND

no load in this experiment(phenomenon occurs)

usual case ±100mA

In LTSPICE simulation, Negative voltage is GND with SHDNN=GND.

But outn have any negative voltage in start-up.

Below is wave image (measurement result).

At INN=-7V, OUTN rise and down to about -6V(not setting voltage).

Probably, SOA protection operated.

I tried to connect 20kΩ from OUTN to OUTP for SOA current (50uA) but the phenomenon don't improve.

When INN voltage slowly rise(6ms),  the phenomenon improve but any INN dip cause OUTN negative voltage(SOA protection?).

SOA protection in Datasheet. 

Best regards 

Thank you very much.

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