MIC2124 Datasheet, PDF (18/24 Pages) Micrel Semiconductor – Constant Frequency, Synchronous Current Mode Buck Controller

Micrel, Inc.
Others
• In order to accurately sense the voltage across the
low-side MOSFET, the LX pin and PGND pin should
be Kelvin connected to the drain and source of the
low-side MOSFET.
• The feedback resistors R_FB1 and R_FB2 (refer to the
typical application schematic on page 1) should be
placed close to the FB pin. The top side of R_FB1
should connect directly to the output node. Run this
trace away from the switch node (junction of Q1, Q2,
and the output inductor).
MIC2124
• The compensation resistor and capacitors should be
placed right next to the COMP pin and the other side
should connect directly to the GND pin on the
MIC2124 rather than going to the plane.
• HSD pin is sensitive to the noise. Too much noise at
HSD pin may cause the jittering at LX. A 10Ω
resistor and 0.1μF capacitor low-pass filter at the
HSD is able to mitigate the noise.
June 2010
18
M9999-060810-D