TPS51396A: current on BST pin

Ning LU 

Ning LU said:

I am not sure What is the maximum current on the BST pin? so i can choose appropriate size of R6, as marked in below's application circuit. Will a R0201 package works fine here?

The current into the BST pin is dominated by the gate-drive current turning on the high-side MOSFET, and is less than 20mA.

0201 (63mW Rating( should be sufficient to handle the required power dissipation.

Ning LU said:

And, since it is a 0 ohm resistor, what is the purpose of putting this resistor here?

Leaving a provision for a resistor in this location allows the value to be increased to a few ohms if needed to slow the turn-on of the switching node to control parasitic ringing on the switching not, either for conducted and/or radiated noise emissions, or peak voltage stress on the switching MOSFETs.  Since the primary contributors to this ringing are layout parasitics, the extent of ringing is generally not known until the board is laid out and built.  A 0Ω resistor allows for mitigation without layout changes.

Thank you Peter, that is a perfect answer.

/Roland