MIC2174_10 Datasheet, PDF (3/27 Pages) Micrel Semiconductor – Synchronous Buck Controller Featuring Adaptive On-Time Control 40V Input, 300kHz

Micrel, Inc.
MIC2174/MIC2174C
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-C