Datasheet

MAX1708
High-Frequency, High-Power, Low-Noise,
Step-Up DC-DC Converter
______________________________________________________________________________________ 13
Layout Considerations
Due to high inductor current levels and fast switching
waveforms, proper PC board layout is essential. Protect
sensitive analog grounds by using a star ground config-
uration. Connect PGND, the input bypass capacitor
ground lead, and the output filter capacitor ground lead
to a single point (star ground configuration). In addition,
minimize trace lengths to reduce stray capacitance and
trace resistance, especially from the LX pins to the catch
diode (D1) and output capacitor (C2) to PGND pins. If an
external resistor-divider is used to set the output voltage
(Figure 4), the trace from FB to the resistors must be
extremely short and must be shielded from switching
signals, such as CLK or LX. To optimize package power
dissipation and minimize device heating under heavy
loads, expand PC trace area connected to the three
PGND pins as much as the layout can allow. This is best
accomplished with a large PGND plane on the surface of
the board. Also note that outer-layer ground plane area
beneath the device provides little heat-sinking benefit. If
an outer-layer ground plane is not feasible, the PGND
pins should be connected to the inner-layer ground
plane with multiple vias (at least three vias per pin is rec-
ommended). Since the purpose of these vias is to opti-
mize thermal conductivity to the inner ground plane, be
sure that the vias have no gaps in their connections to
the ground plane. Refer to a layout example in the
MAX1708EVKIT data sheet.
___________________ Chip Information
SUBSTRATE: GND
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns,
go to www.maxim-ic.com/packages
. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package
drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
16 QSOP E16+1
21-0055 90-0167