UG074 Rev.2.00
Page 10 of 17
Nov 14, 2018
ISL9238EVAL1Z
PCB Layout Guidelines
PIN NUMBER
PIN NAME
LAYOUT GUIDELINES
BOTTOM PAD
33
GND
Connect the ground pad to the ground plane through a low impedance path. Use at least five vias to connect to the
ground planes in the PCB to ensure sufficient thermal dissipation directly under the IC.
1
CSON
Run two dedicated traces with sufficient width parallel to (close to each other to minimize the loop area) the two
terminals of the battery current-sensing resistor to the IC. Place the differential mode and common-mode RC filter
components in the general proximity of the controller.
Route the current-sensing traces through vias to connect the center of the pads, or route the traces into the pads
from the inside of the current-sensing resistor. The following drawings show the two preferred ways of routing
current-sensing traces
.
2
CSOP
3
VSYS
Signal pin that provides feedback for the system bus voltage. Place the optional RC filter in the general proximity of
the controller. Run a dedicated trace from the system bus to the pin and do not route near the switching traces. Do
not share the same trace with the signal routing to the DCIN pin OR diodes.
4
BOOT2
Switching pin. Place the bootstrap capacitor in the general proximity of the controller. Use sufficiently wide trace. Do
not allow any sensitive analog signal traces to cross over or get close to this pin.
5
UGATE2
Run the UGATE2 and PHASE2 traces in parallel with sufficient width. Do not allow any sensitive analog signal traces
to cross over or get close to this pin. Renesas recommends routing the PHASE2 trace to the high-side MOSFET source
pin instead of general copper.
Place the IC close to the switching MOSFET’s gate terminals and keep the gate drive signal traces short for a clean
MOSFET drive. The IC can be placed on the opposite side of the switching MOSFETs.
Place the output capacitors as close as possible to the switching high-side MOSFET drain and the low-side MOSFET
source. Use the shortest PCB trace connection. Place the capacitors on the same PCB layer as the MOSFETs instead
of on different layers and using vias to make the connection.
Place the inductor terminal to the switching high-side MOSFET drain and low-side MOSFET source terminal as close
as possible. Minimize this phase node area to lower the electrical and magnetic field radiation, but make this phase
node area large enough to carry the current. Place the inductor and the switching MOSFETs on the same layer of the
PCB.
6
PHASE2
7
LGATE2
Switching pin. Run the LGATE2 trace parallel to the UGATE2 and PHASE2 traces on the same PCB layer. Use sufficient
width. Do not allow any sensitive analog signal traces to cross over or get close to this pin.
8
VDDP
Place the decoupling capacitor in the general proximity of the controller. Run the trace connecting to the VDD pin
with sufficient width.
9
LGATE1
Switching pin. Run the LGATE1 trace parallel to the UGATE1 and PHASE1 traces on the same PCB layer. Use sufficient
width. Do not allow any sensitive analog signal traces to cross over or get close to this pin.
CURRENT-SENSING TRACES
VIAS
CURRENT-SENSING TRACES
