MAX16838_11 Datasheet, PDF (17/21 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
4.75V TO 40V
L1
Cs
D
CIN
COUT
R2OV
L2
R2EN
R1EN
CVCC
RDRV
CDRV
CCOMP
RCOMP
R1OV
LED
STRINGS
IN
DRAIN
OV
EN
NDRV
CFB
GATE
V_CC
OUT1
OUT2
RISET
DRV
MAX16838
ISET
DIM
COMP
SGND
FLT
CS
RT
PGND LEDGND
R_RT R_CS
Figure 4. SEPIC Configuration
SEPIC Operation
Figure 4 shows a SEPIC application circuit using the
MAX16838. The SEPIC topology is necessary to keep
the output voltage of the DC-DC converter regulated
when the input voltage can rise above and drop below
the output voltage.
Boost-Buck Configuration
Figure 5 shows a boost-buck configuration with the
MAX16838 and MAX15054.
PCB Layout Considerations
LED driver circuits based on the MAX16838 device use
a high-frequency switching converter to generate the
voltage for LED strings. Take proper care while laying
out the circuit to ensure proper operation. The switching-
converter part of the circuit has nodes with very fast volt-
age changes that could lead to undesirable effects on
the sensitive parts of the circuit. Follow these guidelines
to reduce noise as much as possible:
1) Connect the bypass capacitor on VCC and DRV as
close as possible to the device, and connect the
capacitor ground to the analog ground plane using
vias close to the capacitor terminal. Connect SGND
of the device to the analog ground plane using a via
close to SGND. Lay the analog ground plane on the
inner layer, preferably next to the top layer. Use the
analog ground plane to cover the entire area under
critical signal components for the power converter.
2) Have a power ground plane for the switching-
converter power circuit under the power compo-
nents (input filter capacitor, output filter capacitor,
inductor, MOSFET, rectifier diode, and current-
sense resistor). Connect PGND to the power ground
plane as close to PGND as possible. Connect all
other ground connections to the power ground
plane using vias close to the terminals.
______________________________________________________________________________________   17