MAX1553 Datasheet, PDF (9/11 Pages) Maxim Integrated Products – High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs

High-Efficiency, 40V Step-Up
Converters for 2 to 10 White LEDs
Table 1. Component Suppliers
SUPPLIER
Central
Semiconductor
Kamaya
Murata
Nichia
Panasonic
Sumida
Taiyo Yuden
TDK
TOKO
PHONE
WEBSITE
631-435-1110 www.centralsemi.com
260-489-1533
814-237-1431
248-352-6575
714-373-7939
847-956-0666
408-573-4150
847-803-6100
847-297-0070
www.kamaya.com
www.murata.com
www.nichia.com
www.panasonic.com
www.sumida.com
www.t-yuden.com
www.component.tdk.com
www.toko.com
Ensure the diode’s average and peak current ratings
exceed the average output current and peak inductor
current. In addition, the diode’s reverse breakdown
voltage must exceed V_OUT.
Applications Information
Low Input-Voltage Applications
The MAX1553/MAX1554 have minimum input voltages
of 2.7V (MAX1553) and 3.15V (MAX1554). However,
lower battery voltages can still be boosted for LED
drive as long as V_CC remains within the operating
range. Since most systems have a 3.3V system supply
active when the display is active and backlit, that logic
supply can be used to supply V_CC, while the battery
power connects directly to the boost inductor. No bat-
tery current is drawn when EN is low (Figure 4).
PC Board Layout
Due to fast-switching waveforms and high-current
paths, careful PC board layout is required. An evalua-
tion kit (MAX1553EVKIT) is available as an example of
a proper layout.
BATTERY
INPUT
C1
4.7µF
3.3V
LOGIC
C4
0.1µF
ON
OFF
C3
0.1µF
L1
D1
VCC
LX
C2
0.47µF
R2
EN
OV
MAX1553
MAX1554
BRT
FB
SS
GND
R3
R1
WHITE
LEDs
Figure 4. The MAX1553/MAX1554 can drive LEDs from battery
voltages that are lower than the device operating voltage
range by powering V_CC from a logic supply and connecting
the boost inductor to the battery.
When laying out a board, minimize trace lengths
between the IC and the inductor, diode, input capaci-
tor, output capacitor, and R1. Keep traces short, direct,
and wide. Keep noisy traces, such as the LX node
trace, away from FB. Place the V_CC bypass capacitor
(C1) as close to the IC as possible. The ground con-
nections of C1 and C2 should be as close together as
possible. Star connect the grounds for R1, R3, C3, and
the BRT voltage supply as close to the IC as possible.
The traces from V_CC to C1, from C2 to the LEDs, and
from the LEDs to R1 can be longer if required.
Chip Information
TRANSISTOR COUNT: 740
PROCESS: BiCMOS
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