Datasheet

18 Maxim Integrated
Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
MAX16838
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.
Figure 5. Boost-Buck Configuration
Q1
C
1
V
DD
BST
D
1
C
BST
LX
HI
HDRV
GND
MAX15054
R
ISET
R1
OV
R2
OV
C
OUT
LED
STRINGS
R
RT
R
CS
R1
EN
V
IN
R2
EN
C
VCC
D
2
C
DRV
R
DRV
IN GATE NDRV
DRAIN
OV
OUT1
OUT2
ISET
CS
RT
LEDGNDPGNDSGND
COMP
DIM
DRV
CFB
EN
LD3
V
CC
C
IN
R
COMP
C
COMP
FLT
MAX16838