ncp5214 ON Semiconductor, ncp5214 Datasheet - Page 27

• Manufacturer Part Number: ncp5214
• Description: 2-in-1 Notebook Ddr Power Controller
• Manufacturer: ON Semiconductor

PCB Layout Guidelines
high performance and stable operation of the DDR power
controller. The following items must be considered when
preparing PCB layout:
Cautious PCB layout design is very critical to ensure
1. All high−current traces must be kept as short and
2. Power components which include the input
3. To ensure the proper function of the device,
4. The thermal pad of the DFN−22 package should
wide as possible to reduce power loss.
High−current traces are the trace from the input
voltage terminal to the drain of the high−side
MOSFET, the trace from the source of the
high−side MOSFET to the inductor, the trace
from inductor to the VDDQ output terminal, the
trace from the input ground terminal to the
VDDQ output ground terminal, the trace from
VDDQ output to VTTI pin, the trace from VTT
pin to VTT output terminal, and the trace from
VTT output ground terminal to the VTTGND pin.
Power handling and heaksinking of high−current
traces can be improved by also routing the same
high−current traces in the other layers and joined
together with multiple vias.
capacitor, high−side MOSFET, low−side
MOSFET and VDDQ output capacitor of the
buck converter section must be positioned close
together to minimize the current loop. The input
capacitor must be placed close to the drain of the
high−side MOSFET and the source of the
low−side MOSFET.
separated ground connections should be used for
different parts of the application circuit according
to their functions. The input capacitor ground, the
low−side MOSFET source, the VDDQ output
capacitor ground, the VCCP decoupling capacitor
ground should be connected to the PGND. The
trace path connecting the source of the low−side
MOSFET and PGND pin should be minimized.
The VTT output capacitor ground should be
connected to the VTTGND first with a short
trace, it is then connected to the ground plane of
PGND. The VCCA decoupling capacitor ground,
the ground of the VDDQ feedback resistor, the
soft−start capacitor ground, the VTTREF output
capacitor ground should be connected to the
AGND. The AGND pin is then connected directly
through a sense trace to the remote ground sense
point of the PGND, which is usually the ground
of the local bypass capacitor for the load. Never
connect the AGND, PGND and VTTGND
together just under the thermal pad.
be connected to the ground planes in the internal
layer and bottom layer from the copper pad at top
layer underneath the package through six to eight
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NCP5214
27
10. The traces length between the gate driver outputs
12. The copper trace area of the switching node which
13. A snubber circuit consists of a 3.3 W resistor and
14. VTTI should be connected to VDDQ output with
11. To ensure normal function of the device, an RC
5. The input capacitor ground terminal, the VDDQ
6. Sensitive traces like trace from FBDDQ, trace
7. Separate sense trace should be used to connect
8. Separate sense trace should be used to connect the
9. Separate sense trace should be used to connect
vias with 0.6 mm hole−diameter to help heat
dissipation and ensure good thermal capability. It
is recommended to use PCB with 1 oz or 2 oz
copper foil. The thermal pad can be connected to
either PGND ground plane or AGND ground
plane but not both.
output capacitor ground terminal and the source
of the low−side MOSFET must be connected to
the PGND ground plane through multiple vias.
from COMP, trace from OCDDQ, trace from
FBVTT and trace from VTTREF should be
avoided from the high−voltage switching nodes
like SWDDQ, BOOST, TGDDQ and BGDDQ.
the VDDQ point of regulation, which is usually
the local bypass capacitor for load, to the
feedback resistor divider to ensure accurate
voltage sensing. The feedback resistor divider
should be place close to the FBDDQ pin.
VTT point of regulation, which is usually the local
bypass capacitor for load, to the FBVTT pin.
the VDDQ point of regulation to the DDQREF
pin to ensure that the reference voltage to VTT is
accurately half of the VDDQ voltage.
and gates of the MOSFETs must be minimized to
avoid parasitic impedance.
filter should be placed close to the VCCA pin and
a decoupling capacitor should be placed close to
the VCCP pin.
includes the source of the high−side MOSFET,
drain of the low−side MOSFET and high voltage
side of the inductor should be minimized by using
short wide trace to reduce EMI.
1.0 nF capacitor may need to be connected across
the switching node and PGND to reduce the
high−frequency ringing occurring at the rising
edge of the switching waveform to obtain more
accurate inductor current limit sensing of the
VDDQ buck converter. However, adding this
snubber circuit will slightly reduce the conversion
efficiency.
wide and short trace if VDDQ is used as the
sourcing supply for VTT. An input capacitor of at
least 10 mF should be added close to the VTTI
pin and bypassed to VTTGND if external voltage
supply is used as the VTT sourcing supply.