BL9581
36V, 1.2A Step-down
High Brightness LED Driver with Internal Switch
FEATURES
Simple low parts count
Internal 36V NDMOS switch
Up to 1.2A output current
Single pin on/off and brightness control
using DC voltage or PWM
Soft Start
High efficiency (up to 97%)
Wide input voltage range: 6V to 36V
Output shutdown
Up to 1MHz switching frequency
Inherent open-circuit LED protection
Typical 3% output current accuracy
High-side current sense
Hysteretic control: no compensation
Adjustable constant LED current
Over temperature protection
Pb-free SOT23-5 packages
DESCRIPTION
The BL9581 is a continuous mode inductive
step-down converter, designed for driving
single or multiple series connected LEDs
efficiently from a voltage source higher than
the LED voltage. The device operates from
an input supply between 6V and 36V and
provides an externally output current up to
1.2A. Depending upon supply voltage and
external components, this can provides up to
24 watts of output power.
The BL9581 includes the output switch and a
high-side output current sensing circuit, which
uses an external resistor to set the nominal
average output current.
Output current can be adjusted by applying
an external control signal to the 'ADJ' pin.
The ADJ pin will accept either a DC voltage
or a PWM waveform. During DC dimming,
this will provide a continuous output current
that is proportional to the external applied DC
voltage. During the PWM dimming, this will
provide a gated output current and the
average current is proportional to the duty
cycle. Applying a voltage of 0.2V or lower to
the ADJ pin turns the output off and switches
the device into a low current standby state.
APPLICATIONS
Low voltage halogen replacement LEDs
Automotive lighting
Low voltage industrial lighting
LED back-up lighting
Illuminated signs
LCD TV backlighting
ORDERING INFORMATION
BL9581
X XXX
Package:
RN: SOT23--5
Features:
P: Standard (default, lead free)
C: Customized
TYPICAL APPLICATION
Rs
V
IN
(6V-36V)
0.1ohm
C1
4.7uF
D1
L1
47uH
V
IN
N/C
GND
ADJ
I
SENSE
BL9581
GND
LX
PPMIC BU
BL9581 Rev 1.3
2/2010
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