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PDF MAX1698EUB Data sheet ( Hoja de datos )
| Número de pieza | MAX1698EUB | |
| Descripción | High-Efficiency Step-Up Current Regulator for LEDs | |
| Fabricantes | Maxim Integrated | |
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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
VCC 1
SHDN 2
REF 3
ADJ 4
GND 5
MAX1698
µMAX
10 EXT
9 CS
8 PGND
7 GND
6 FB
Typical Operating Circuit
VBATT
L
VCC VCC
EXT
ON MAX1698
OFF
SHDN
CS
REF PGND
ADJ
FB
GND
D1
ILED
RFB RN
VOUT
COUT
________________________________________________________________ Maxim Integrated Products 1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
1 page  
High-Efficiency Step-Up
Current Regulator for LEDs
Pin Description
PIN NAME
FUNCTION
1 VCC IC Supply Voltage Input. Power for internal circuitry. Input range is 2.7V to 5.5V.
Active-Low Shutdown Input. In shutdown, the MOSFET turns off, but a current path still exists between the
2 SHDN input and output. The minimum forward voltage of the LED array must exceed the maximum VBATT to ensure
that the LEDs are off in shutdown.
3
REF
1.25V Reference Output. Capable of sourcing 150µA for external loads. This pin is internally compensated.
Do not connect any bypass capacitors at REF.
4 ADJ Adjust Input. Allows dynamic adjustment of the output current. FB regulates to 300mV when ADJ = REF.
5, 7 GND Ground
6 FB Feedback Input. Connect to the external LED current-sense feedback resistor.
8 PGND Power Ground
9 CS FET Current-Sense Input
10 EXT Gate Driver Output
SHDN
VCC
ADJ
UNDERVOLTAGE
LOCKOUT/
SHUTDOWN
MAX1698
MAX tON
MIN tOFF
CS
VL
VCC
EXT
PGND
FB
GND
Figure 1. Functional Diagram
SOFT-START
1.25V REFERENCE
REF
_______________________________________________________________________________________ 5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MAX1698EUB.PDF ] | |
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