
19-0865; Rev 3; 8/10
ATION
EVALU
AVAILA
KIT
B LE
Highest Efficiency Supply for 2 to 6
Series WLEDs in a 2mm x 2mm TDFN Package
General Description
The MAX8901A/MAX8901B step-up converters drive from
two to six series-connected white LEDs (WLEDs) with
constant current to provide uniform WLED intensity for
LCD backlighting in cell phones, PDAs, and other hand-
held devices. The MAX8901_ operate at a fixed 750kHz
(typ) switching frequency, allowing for tiny external com-
ponents, and are optimized for the highest possible effi-
ciency over the full 1-cell Li+/Li-Poly battery range.
These converters use a single input (ON) to enable the
IC and to control WLED intensity. The MAX8901A
requires a direct PWM input to regulate WLED intensity
with the WLED current proportional to the PWM duty
cycle. The MAX8901B uses single-wire, serial-pulse
dimming that reduces the WLED intensity in 32 linear
steps. Full-scale WLED current for serial-pulse
dimming is 24.75mA (MAX8901B, 0.75mA/step).
The MAX8901_ feature an internal soft-start to eliminate
inrush currents during startup, input overvoltage
protection, WLED overvoltage protection, and a shut-
down mode with 0.01μA (typ) shutdown current. No
WLED current is present in shutdown provided the
WLED forward voltage is greater than the input supply
Features
o High Efficiency, Up to 91%
o 2.6V to 5.5V Input Voltage Range
o Fixed-Frequency Operation
o Supplies from 2 to 6 WLEDs with 1.3% LED Current
Accuracy
o Flexible Dimming Control
Direct PWM Dimming (MAX8901A)
32-Step, Single-Wire Serial Dimming
(MAX8901B)
o Input Undervoltage Lockout
o Input Overvoltage Lockout
o WLED Overvoltage Protection (25V typ)
o 0.01μA (typ) Shutdown Current
o No WLED Current in Shutdown
o Internal Soft-Start and Thermal Shutdown
Ordering Information
voltage. Additional features include undervoltage lock-
out (UVLO) and thermal shutdown.
The MAX8901_ are available in tiny 8-pin, 2mm x 2mm
TDFN-EP packages (0.8mm max height).
Applications
PART
MAX8901A ETA+T
MAX8901B ETA+T
PIN-PACKAGE
8 TDFN-EP*
2mm x 2mm
8 TDFN-EP*
2mm x 2mm
TOP MARK
+ABA
+ABB
Display Backlight (from 2 to 6 WLEDs)
Cellular Phones
PDAs and Smartphones
MP3 and Portable Media Players
Portable Navigation Devices
Digital Cameras
INPUT
2.6V TO 5.5V
Note: All devices are specified over the -40°C to +85°C operating
temperature range.
+ Denotes a lead(Pb)-free/RoHS-compliant package.
* EP = Exposed pad.
T = Tape and reel.
Pin Configuration appears at end of data sheet.
Typical Operating Circuits
INPUT
2.6V TO 5.5V
3
IN
LX
4
OUTPUT
UP TO 25V
3
IN
LX
4
OUTPUT
UP TO 25V
MAX8901A
7
COMP
OVP
1
7
COMP
MAX8901B
OVP
1
PWM DIMMING
CONTROL
6
GND
PGND
5
SERIAL-PULSE
DIMMING
6
GND
PGND
5
CONTROL
2
ON
EP
CS
8
2
ON
EP
CS
8
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
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