MAX8901A Datasheet, PDF (1/15 Pages) Maxim Integrated Products – Highest Efficiency Supply for 2 to 6 Series WLEDs in a 2mm x 2mm TDFN Package

19-0865; Rev 0; 8/07
EVAALVUAAILTAIOBNLEKIT
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_ features 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
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
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
PWM DIMMING
CONTROL
3
IN
LX ⁴
7
MAX8901A
COMP
1
OVP
6
GND
5
PGND
2 _ON
8
EP
CS
OUTPUT
UP TO 25V
Features
♦ High Efficiency, Up to 91%
♦ 2.6V to 5.5V Input Voltage Range
♦ Fixed-Frequency Operation
♦ Supplies from 2 to 6 WLEDs with 1% LED Current
Accuracy
♦ Flexible Dimming Control
Direct PWM Dimming (MAX8901A)
32-Step, 1-Wire Serial Dimming
(MAX8901B)
♦ Input Undervoltage Lockout
♦ Input Overvoltage Lockout
♦ WLED Overvoltage Protection (25V typ)
♦ 0.01µA (typ) Shutdown Current
♦ No WLED Current in Shutdown
♦ Internal Soft-Start and Thermal Shutdown
Ordering Information
PART
PIN-PACKAGE ^PKG
CODE
TOP
MARK
MAX8901AETA+T
8 TDFN-EP*
2mm x 2mm
T822-1 +ABA
MAX8901BETA+T
8 TDFN-EP*
2mm x 2mm
T822-1 +ABB
Note: All devices are specified over the -40°C to +85°C operating
temperature range.
+Denotes a lead-free package.
*EP = Exposed paddle.
T = Tape and reel.
Pin Configuration appears at end of data sheet.
Typical Operating Circuits
INPUT
2.6V TO 5.5V
SERIAL-PULSE
DIMMING
CONTROL
3
IN
LX ⁴
MAX8901B
7
COMP
1
OVP
6
GND
5
PGND
2 _ON
EP
CS ⁸
OUTPUT
UP TO 25V
________________________________________________________________ Maxim Integrated Products 1
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.