THVD1552: Design external ESD protection for RS485

Tool/software:

Hello TI Team,

i want to design an external ESD protection for RS485 communication. 

I'm using the THVD1552D which has an internal ESD protection circuit according to the datasheet:

"Internal ESD protection circuits of the THVD15xx protect the transceivers against electrostatic discharges (ESD)
according to IEC 61000-4-2 [...]"

We want to connect a external TVS device like the ESDS552 with a bi-directional surge protection and stand-off voltage of -12V to 12V suited for a RS485 network.

But I can't find any further information from the internal ESD protection like the stand-off or breakdown voltage from the THVD1552D. I want to make sure that the internal ESD doesn't interfere with the external ESD protection.

Is there any information about the characteristic of the ESD protection circuit of the THVD15xx?  And can I use the ESDS552 to protect the Network or is it not recommended because of the internal ESD protection of the THVD1552 whose breakover voltage is below the one from the ESDS552?

Best Regards 

Marcel