MIC2164_10 Datasheet, PDF (3/39 Pages) Micrel Semiconductor – Synchronous Buck Controllers Featuring Adaptive On-Time Control 28V Input, Constant Frequency

Micrel, Inc.
MIC2164/-2/-3/C
Pin Description (Continued)
Pin Number
9
10
Pin Name
LX
BST
Pin Function
Switch Node and Current Sense input: High current output driver return. The LX pin connects directly
to the switch node. Due to the high speed switching on this pin, the LX pin should be routed away from
sensitive nodes. LX pin also senses the current by monitoring the voltage across the low-side
MOSFET during OFF time. In order to sense the current accurately, connect the low-side MOSFET
drain to LX using a Kelvin connection.
Boost (output): Bootstrapped voltage to the high-side N-channel MOSFET driver. A Schottky diode is
connected between the IN pin and the BST pin. A boost capacitor of 0.1μF is connected between the
BST pin and the LX pin. Adding a small resistor in series with the boost capacitor can slow down the
turn-on time of high-side N-Channel MOSFETs.
September 2010
3
M9999-091310-D