MIC2128 Datasheet, PDF (26/32 Pages) Microchip Technology – 75V, Synchronous Buck Controller Featuring Adaptive On-Time Control with External Soft Start

MIC2128
6.0 PCB LAYOUT GUIDELINES
PCB layout is critical to achieve reliable, stable and
efficient performance. The following guidelines should
be followed to ensure proper operation of the
MIC2128converter.
6.1 IC
• The ceramic bypass capacitors, which are con-
nected 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.
6.3 Inductor
• 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 feed-
back (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 and
wide. The ground plane should be the connection
between the MOSFET source and PGND.
• Chose a low-side MOSFET with a high CGS/CGD
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.
DS20005620A-page 26
 2016 Microchip Technology Inc.