BL8545 Datasheet, PDF (1/6 Pages) SHANGHAI BELLING CO., LTD. – Max. 3MHz, Variable Frequency Step-up DC/DC Converter

BL8545
Max. 3MHz, Variable Frequency Step-up DC/DC Converter
DESCRIPTION
The BL8545 variable frequency step-up
Converter drives white LEDs with a constant
current to provide backlight in cell phones,
PDAs, and other hand-held devices. It
features allowing series connection of the
white LEDs so that the LED currents are
identical for uniform brightness. An enable
input can be pulsed repeatedly to adjust
LEDs brightness. The fast 3MHz operation
frequency allows for smaller capacitor and
inductor. Fault condition protection uses
cycle-by cycle current limiting to sense
maximum inductor current and over-voltage
protection. The 0.2V low reference voltage
minimized the power loss across the current
sense resistor.
FEATURES
 Up to 24V Output Voltage
 Wide Operation Range: 2V to 6V
 Maximum 3MHz Operating Frequency
 PWM Dimming Control
 Shutdown Current <1uA
 Current Limit Cycle-by-Cycle
 Low Current Sense Threshold: 200mV
 24V Over Output Voltage Protection
 Compact SOT23-6 Package
APPLICATIONS
 Compact Back Light Module
 Power Source for LED
 Constant Current Source
The converter can operate from 2V to 6V,
and capable of delivering maximum 200mA
output current at 4-LEDs application with 3V
input voltage. Quiescent current drawn from
power source is as low as 120uA. All of these
features make BL8545 be suitable for the
portable devices, which are supplied by a
single battery.
BL8545 is available in SOT23-6 package that
is PB free.
TYPICAL APPLICATION
L1
D1
VIN
10uH
SS14
Cin
4.7uF
ON
OFF
VIN
LX
OVP
BL^L8^C5³³4⁰5⁰
CE
FB
GND
Cout
4.7uF
LED1
LED2
LED3
LED4
R1
LED17
LED18
LED19
LED20
R5
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Figure1. BL8545 Typical Application Circuit
1