MAX16838_11 Datasheet, PDF (18/21 Pages) Maxim Integrated Products – Integrated, 2-Channel, High-Brightness LED Driver with High-Voltage Boost and SEPIC Controller

Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
3) There are two loops in the power circuit that carry
high-frequency switching currents. One loop is
when the MOSFET is on—from the input filter
capacitor positive terminal, through the inductor, the
internal MOSFET, and the current-sense resistor, to
the input capacitor negative terminal. The other loop
is when the MOSFET is off—from the input capacitor
positive terminal, through the inductor, the rectifier
diode, output filter capacitor, to the input capaci-
tor negative terminal. Analyze these two loops and
make the loop areas as small as possible. Wherever
possible, have a return path on the power ground
plane for the switching currents on the top layer
copper traces, or through power components. This
reduces the loop area considerably and provides
a low-inductance path for the switching currents.
Reducing the loop area also reduces radiation dur-
ing switching.
4) Connect the power ground plane for the constant-
current LED driver part of the circuit to LEDGND as
close as possible to the device. Connect SGND to
PGND at the same point.
VIN
C₁
CIN
R1EN
R2_EN
CVCC
RDRV
CDRV
RCOMP
CCOMP
D₁
VDD
BST
MAX15054 _HDRV
GND
HI
LX
CBST
Q1
L
D2
D3
C_OUT
R1OV
IN
EN
GATE NDRV
DRAIN
R2OV
CFB
OV
VCC
OUT1
OUT2
R_ISET
DRV
MAX16838
ISET
DIM
COMP
SGND
PGND
FLT
CS
RT
LEDGND
R_RT R_CS
LED
STRINGS
Figure 5. Boost-Buck Configuration
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