MAX8901A Datasheet, PDF (8/15 Pages) Maxim Integrated Products – Highest Efficiency Supply for 2 to 6 Series WLEDs in a 2mm x 2mm TDFN Package

Highest Efficiency Supply for 2 to 6
Series WLEDs in a 2mm x 2mm TDFN Package
MAX8901A
THERMAL
SHUTDOWN
INTERNAL
750kHz OSC
SHUTDOWN
TIMER
REF
BOOST
CONTROL
LOGIC
GND
IC
IN
POWER
LX
PGND
OVP
Gm
D*0.5V
EP
CS
PWM
COMP
ON
Figure 2. MAX8901A Block Diagram
Detailed Description
The high efficiency and tiny size of the MAX8901A/
MAX8901B WLED step-up converters make them ideally
suited for driving LCD backlighting in cell phones, PDAs,
and other portable and handheld devices. The
MAX8901_ drive from 2 to 6 series-connected WLEDs
with constant current for uniform WLED intensity and are
optimized for the highest possible efficiency (up to 91%)
over the full 1-cell Li+/Li-Poly battery range. These tiny
2mm x 2mm devices operate at a constant 750kHz
switching frequency, and use small external components
to achieve minimal input and output ripple while occupy-
ing the smallest possible footprint.
These converters use a single input (ON) to enable the IC
and to control WLED intensity. The MAX8901A requires a
direct PWM input to modulate WLED intensity, with WLED
current proportional to the PWM duty cycle. The
MAX8901B uses single-wire, serial-pulse dimming that
reduces the WLED intensity in 32 equal steps. Full-scale
WLED current for serial-pulse dimming is 24.75mA.
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