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A8180 Schematic ( PDF Datasheet ) - AiT Semiconductor

Teilenummer A8180
Beschreibung 1.4A STEP-DOWN LED DRIVER
Hersteller AiT Semiconductor
Logo AiT Semiconductor Logo 




Gesamt 20 Seiten
A8180 Datasheet, Funktion
AiT Semiconductor Inc.
www.ait-ic.com
A8180
36V, 1.4A STEP-DOWN LED DRIVER
HIGH BRIGHTNESS WITH INTERNAL SWITCH
DESCRIPTION
The A8180 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 1.4A. Depending upon supply
voltage and external components, this can provides up
to 24 watts of output power.
The A8180 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.
FEATURES
Simple low parts count
Internal 36V NDMOS switch
Up to 1.4A 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
Available in SOT-89-5 and SOP8 packages
APPLICATIONS
Low voltage halogen replacement LEDs
Automotive lighting
Low voltage industrial lighting
LED back-up lighting
Illuminated signs
LCD TV backlighting
The A8180 is available in SOT-89-5 and SOP8
Packages.
TYPICAL APPLICATION
ORDERING INFORMATION
Package Type
Part Number
SOT89-5
SOP8
Note
K5
A8180K5R
A8180K5VR
M8
A8180M8R
A8180M8VR
V: Green Package
R : Tape & Reel
AiT provides all Pb free products
Suffix “ V “ means Green Package
REV1.1
- APR 2010 RELEASED, MAR 2011 REVISED -
-1-






A8180 Datasheet, Funktion
AiT Semiconductor Inc.
www.ait-ic.com
A8180
36V, 1.4A STEP-DOWN LED DRIVER
HIGH BRIGHTNESS WITH INTERNAL SWITCH
7. Operating Frequency Vs. Supply Voltage
L=47uH
8. Duty Cycle Vs. Supply Voltage
L=47uH
9. Output Current Vs. Supply Voltage
L=47uH
10. Output Current variation Vs. Supply Voltage
L=100uH
11. Operating Frequency Vs. Supply Voltage
L=100uH
12. Duty Cycle Vs. Supply Voltage
L=100uH
REV1.1
- APR 2010 RELEASED, MAR 2011 REVISED -
-6-

6 Page









A8180 pdf, datenblatt
AiT Semiconductor Inc.
www.ait-ic.com
The average output current is given by:
A8180
36V, 1.4A STEP-DOWN LED DRIVER
HIGH BRIGHTNESS WITH INTERNAL SWITCH
Note that 100% brightness setting corresponds to: (1.3V≤VADJ≤5V)
Output Current Adjustment by PWM Control
A Pulse Width Modulated (PWM) signal with duty cycle PWM can be applied to the ADJ pin, as shown below,
to adjust the output current to a value below the nominal average value set by resistor RS:
PWM dimming provides reduced brightness by modulating the LED’s forward current between 0% and
100%.The LED brightness is controlled by adjusting the relative ratios of the on time to the off time. A 25%
brightness level is achieved by turning the LED on at full current for 25% of one cycle. To ensure this
switching process between on and off state is invisible by human eyes, the switching frequency must be
greater than 100 Hz. Above 100 Hz, the human eyes average the on and off times, seeing only an effective
brightness that is proportional to the LED’s on-time duty cycle. The advantage of PWM dimming is that the
REV1.1
- APR 2010 RELEASED, MAR 2011 REVISED -
- 12 -

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