MAX1698 Datasheet, PDF (1/8 Pages) Maxim Integrated Products – High-Efficiency Step-Up Current Regulator for LEDs

19-1621; Rev 0; 1/00
EVAALVUAAILTAIOBNLEKIT
High-Efficiency Step-Up
Current Regulator for LEDs
General Description
The MAX1698 is the most efficient driver for white or
color LEDs. The device is ideal for LED backlit displays
in PDAs and digital cameras, and can also be used for
larger displays like those in laptop computers. Its
numerous benefits include greater simplicity, lower
cost, higher efficiency, longer bulb life, and greater reli-
ability when compared to fluorescent (CCFL) and elec-
troluminescent (EL) lamps.
The MAX1698 is a switch-mode boost controller in
which LED current, rather than output voltage, provides
the feedback signal. It can operate with battery inputs
as low as 0.8V. The device drives series-connected
LEDs with a controlled current that is measured at a
sense resistor connected at the feedback pin. The
required sense resistor is typically 15Ω, not an expen-
sive fractional-ohm value. LED current control and dim-
ming are accomplished with an adjust input (ADJ), not
with lossy current-limiting resistors. For larger light out-
put, multiple LED banks can be connected in parallel
with up to 5W total output power.
The MAX1698 is supplied in a space-saving 10-pin
µMAX package that occupies half the space of an 8-pin
SO. An evaluation kit (MAX1698EVKIT) is available to
speed designs.
Applications
Battery-Powered Backlight Applications
Backlight for LCD Panels
Cell Phones
Handy Terminals
PDAs
Features
o Over 90% Efficiency
o Lossless, Adjustable LED Brightness
o Space-Saving 10-Pin µMAX Package
o Simpler, Lower Cost, More Reliable Compared
to CCFL or EL Backlights
o Up to 5W Output Power
PART
MAX1698EUB
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
10 µMAX
TOP VIEW
Pin Configuration
V_CC 1
SHDN 2
REF 3
ADJ 4
GND 5
MAX1698
µMAX
10 EXT
9 CS
8 PGND
7 GND
6 FB
Typical Operating Circuit
L
V_BATT
V_CC
V_CC
EXT
ON
MAX1698
OFF
SHDN
CS
REF
PGND
ADJ
FB
GND
D1
I_LED
R_FB
R_N
V_OUT
C_OUT
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