Thank you for contacting Cypress.
You can calculate the maximum operating junction temperature for our devices using the below formula :
Tj = (Theta Ja * P) + Ta
Tj : Junction temperature
Theta Ja : Junction to ambient thermal resistance
P : Power consumption of the device (Operating Voltage * Operating Current)
Ta : Ambient temperature
Please note that the Theta Ja value for S25FL128SAGBHI300 is 38 °C/W.
You can refer to the following application note for more details : https://www.cypress.com/file/210756/download
Please let us know if you have any further queries.
I was also wondering if you have any data on the Maximum Junction temperature the device can support?(not operating Tj)