BL9590
Six-String White LED Driver with Active Current
Balancing for LCD panel Applications
FEATURES
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Drives Six Parallel Strings with Multiple Series-
Connected LEDs per String
±1.5% Current Regulation Accuracy Between
Strings
Low 450mV Feedback Voltage at Full Current
Improves Efficiency
Step-Up Controller Regulates the Output Just
Above the Highest LED String Voltage
Full-Scale LED Current Adjustable from 15mA
to 25mA, or Preset 20mA
Wide 100:1 Dimming Range
Programmable Dimming Control: Direct DPWM
or Analog Dimming
Built-In PLL for Synchronized Dimming Control
Open and Short LED Protections
Output Overvoltage Protection
Wide Input Voltage Range from 4.5V to 26V
External MOSFET Allows a Large Number of
LEDs per String
500kHz/750kHz/1MHz Switching Frequency
Small, 20-Pin, 4mm x 4mm Thin QFN Package
APPLICATIONS
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Notebook, Subnotebook, and Tablet Computer
Displays
Automotive Systems
Handy terminals
DESCRIPTION
The BL9590 is a high-efficiency driver for white
light-emitting diodes (LEDs). It is designed for large
liquid-crystal displays (LCDs) that employ an array
of LEDs as the light source. A current-mode step-up
controller drives up to six parallel strings of multiple
series-connected LEDs. Each string is terminated
with ballast that achieves ±1.5% current regulation
accuracy, ensuring even brightness for all LEDs.
The BL9590 has a wide input-voltage range from
4.5V to 26V, and provides a fixed 20mA or
adjustable 15mA to 25mA full-scale LED current.
The BL9590 has two dimming control modes to
enable a wide variety of applications. In direct
DPWM mode, the LED current is directly turned on
and off by a PWM signal. In analog dimming mode,
an internal phase-locked loop (PLL) circuit
translates the PWM signal into an analog signal and
linearly controls the LED current down to 12.5%.
Below 12.5%, digital dimming is added to allow
lower average LED current down to 1%. Both
control methods provide 100:1 dimming range. The
BL9590 has multiple features to protect the
controller from fault conditions. Separate feedback
loops limit the output voltage if one or more LEDs
fail open or short. The controller features cycle-by-
cycle current limit to provide consistent operation
and soft-start capability. A thermal shutdown circuit
provides another level of protection. The step-up
controller uses an external MOSFET, which
provides good efficiency and allows for scalable
output power and maximum operating voltage. Low
feedback voltage at each LED string (450mV) helps
reduce power loss. The BL9590 features selectable
switching frequency (500kHz, 750kHz, or 1MHz),
which allows trade-offs between external com-
ponent size and operating efficiency. The BL9590 is
available in a thermally enhanced, lead-free, 20-pin,
4mm x 4mm, Thin QFN package.
ORDERING INFORMATION
BL9590 –X XXX
Package:
Q20: QFN20
T20: TQFN20
Features:
P: Standard (default, lead free)
C: Customized
TYPICAL APPLICATION
PPMIC BU
BL9590 Rev 0.3
3/2010
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