ADP3208 ON Semiconductor, ADP3208 Datasheet - Page 37

• Manufacturer Part Number: ADP3208
• Description: 7-bit, Programmable, Dual-phase, Mobile, Cpu, Synchronous Buck Controller
• Manufacturer: ON Semiconductor

2.
3.
path for two reasons: it minimizes the inductance in the
switching loop, which can cause high energy ringing, and it
accommodates the high current demand with minimal
voltage loss.
When a power-dissipating component (for example, a
power MOSFET) is soldered to a PCB, the liberal use of
vias, both directly on the mounting pad and immediately
surrounding it, is recommended. Two important reasons
for this are improved current rating through the vias and
improved thermal performance from vias extended to the
opposite side of the PCB, where a plane can more readily
transfer heat to the surrounding air. To achieve optimal
thermal dissipation, mirror the pad configurations used to
heat sink the MOSFETs on the opposite side of the PCB. In
addition, improvements in thermal performance can be
obtained using the largest possible pad area.
The output power path should also be routed to encompass
a short distance. The output power path is formed by the
current path through the inductor, the output capacitors,
and the load.
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4.
Signal Circuitry
1.
2.
3.
For best EMI containment, a solid power ground plane
should be used as one of the inner layers and extended
under all power components.
The output voltage is sensed and regulated between the FB
and FBRTN pins, and the traces of these pins should be
connected to the signal ground of the load. To avoid
differential mode noise pickup in the sensed signal, the
loop area should be as small as possible. Therefore, the FB
and FBRTN traces should be routed adjacent to each other,
atop the power ground plane, and back to the controller.
The feedback traces from the switch nodes should be
connected as close as possible to the inductor. The CSREF
signal should be Kelvin connected to the center point of
the copper bar, which is the V
inductors of all the phases.
On the back of the ADP3208 package, there is a metal pad
that can be used to heat sink the device. Therefore, running
vias under the ADP3208 is not recommended because the
metal pad may cause shorting between vias.
CORE
common node for the
ADP3208