TPS563210A: what is high side FET VDS rating

user4979989  Allen,

Since the VIN to SW rating is not listed separately, it's a safe assumption that theirAbsmax ratings will be similar, 19V DC 21V for <10ns transient.

Keep in mind, the Absolute Maximum rating is not the same as a Vds breakdown rating.  The Absmax rating will always be lower than the breakdown voltage, though the amount of margin can vary from design to design and with normal processing variations.  The actual breakdown voltage will all be above the 19V rating with typical break-down voltages a few volts higher. 

A word of caution testing the exact Vds break-down - keep the source current for testing the break-down small, recommended less than 100μA with as little external capacitance as possible while testing.  There are additional circuits attached to the VIN net that could avalanche before the primary power FETs during a slowly rizing VIN above 21V, and the FETs can experience "Snap-Back" after exceeding their break-down voltage.  During Snap-back, the avalanche voltage of the MOSFET decreases, which can discharge external capacitance and a large external capacitor could deliver excessive energy to the FET devices, damaging them.

During a fast rising VIN (<10ns) such as an ESD event, the primary MOSFETs or the ESD protection devices will trigger first first, and hold the VIN voltage below the threshold of these other, lower current paths until the ESD energy is dissipated, but during a slowly rising DC threshold test, process variations can result in those other paths triggering first.