MIC2125 Datasheet, PDF (25/34 Pages) Microchip Technology – 28V Synchronous Buck Controllers Featuring Adaptive ON-Time Control

MIC2125/6
6.0 PCB LAYOUT GUIDELINES
6.3 Inductor
PCB layout is critical to achieve reliable, stable and
efficient performance. The following guidelines should
be followed to ensure proper operation of the
MIC2125/26 converter.
6.1 IC
• The ceramic bypass capacitors which are
connected to the V_DD and P_VDD pins must be
located right at the IC. Use wide traces to connect
to the V_DD, P_VDD and A_GND, P_GND pins
respectively.
• The signal ground pin (A_GND) must be connected
directly to the ground planes.
• Place the IC close to the point-of-load (POL).
• Signal and power grounds should be kept
separate and connected at only one location.
6.2 Input Capacitor
• Place the input ceramic capacitors as close as
possible to the MOSFETs.
• Place several vias to the ground plane close to
the input capacitor ground terminal.
• Keep the inductor connection to the switch node
(SW) short.
• Do not route any digital lines underneath or close
to the inductor.
• Keep the switch node (SW) away from the
feedback (FB) pin.
• The SW pin should be connected directly to the
drain of the low-side MOSFET to accurately
sense the voltage across the low-side MOSFET.
6.4 Output Capacitor
• Use a copper plane to connect the output
capacitor ground terminal to the input capacitor
ground terminal.
• The feedback trace should be separate from the
power trace and connected as close as possible
to the output capacitor. Sensing a long
high-current load trace can degrade the DC load
regulation.
6.5 MOSFETs
• MOSFET gate drive traces must be short. The
ground plane should be the connection between
the MOSFET source and P_GND.
• Choose a low-side MOSFET with a high C_GS/C_GD
ratio and a low internal gate resistance to
minimize the effect of d_v/d_t inducted turn-on.
• Use a 4.5V V_GS rated MOSFET. Its higher gate
threshold voltage is more immune to glitches than
a 2.5V or 3.3V rated MOSFET.
For more information about the Evaluation board layout, please contact Microchip sales.
 2015 Microchip Technology Inc.
DS20005459B-page 25