MAX16821A/MAX16821B/MAX16821C
PCB Layout
Use the following guidelines to layout the LED driver.
1) Place the IN, V
CC
, and V
DD
bypass capacitors
close to the MAX16821A/MAX16821B/MAX16821C.
2) Minimize the area and length of the high-current
switching loops.
3) Place the necessary Schottky diodes that are con-
nected across the switching MOSFETs very close to
the respective MOSFET.
4) Use separate ground planes on different layers of
the PCB for SGND and PGND. Connect both of
these planes together at a single point and make
this connection under the exposed pad of the
MAX16821A/MAX16821B/MAX16821C.
5) Run the current-sense lines CSP and CSN very
close to each other to minimize the loop area. Run
the sense lines SENSE+ and SENSE- close to each
other. Do not cross these critical signal lines with
power circuitry. Sense the current right at the pads
of the current-sense resistors. The current-sense
signal has a maximum amplitude of 27.5mV. To pre-
vent contamination of this signal from high dv/dt
and high di/dt components and traces, use a
ground plane layer to separate the power traces
from this signal trace.
6) Place the bank of output capacitors close to the load.
7) Distribute the power components evenly across the
board for proper heat dissipation.
8) Provide enough copper area at and around the
switching MOSFETs, inductor, and sense resistors
to aid in thermal dissipation.
9) Use 2oz or thicker copper to keep trace inductances
and resistances to a minimum. Thicker copper con-
ducts heat more effectively, thereby reducing thermal
impedance. Thin copper PCBs compromise efficiency
in applications involving high currents.
High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
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Selector Guide
