CASC
AEROSEMI
1.2MHz, High Efficiency
Boost White LED Driver
GENERAL DESCRIPTION
The MT9284 is a step-up converter designed for
driving up to 7 series white LEDs from a single cell
Lithium Ion battery. The MT9284 uses current
mode, fixed frequency architecture to regulate an
LED current, which is measured through an
external current sense resistor.
The MT9284 includes under-voltage lockout,
current limiting and thermal overload protection
preventing damage in the event of an output
overload.
Optimized operation frequency can meet the
requirement of small LC filters value and low
operation current with high efficiency. Internal soft
start function can reduce the inrush current. Tiny
package type provide the best solution for PCB
space saving and total BOM cost.
MT9284
FEATURES
High Efficiency: Up to 90%
1.2MHz Constant Frequency Operation
Integrated internal Power MOSFET
Drives up to 7 Series WLEDs
Soft-start/Dimming with wide Frequency
Range
UVLO, Thermal Shutdown
Internal Current limit
Over Voltage Protection
Small LC Filter
Minimize the External Component
<1µA Shutdown Current
SOT23-6 Package
APPLICATIONS
Camera Flash White LED
Mobile Phone, Smart Phone LED Backlight
PDA LED Backlight
Digital Still Cameras
Camcorder
TYPICAL APPLICATION
20
V
IN
C
IN
1μF
L 4.7μH to 22μH
D
C
OUT
1μF
7 WLEDs
LED Current vs. PWM Dimming
V
OUT
15
I
LED
(mA)
VIN
SW
MT9284 OV
10
EN
GND
FB
R
CS
5
F=100kHz
7S1P WLEDs
0
Figure 1. Basic Application Circuit
0
20
40
60
80
100
PWM Duty Cycle(%)
MT9284 Rev1.0
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AEROSEMI
MT9284 1.2MHz,High Efficiency Boost White LED Driver
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Supply Voltage……………….-0.3V to 6V
EN,FB Voltages……………………..-0.3V to 6V
SW Voltage………………………..-0.3V to 30V
Power Dissipation………………………...0.6W
Thermal Resistance
θ
JC
……………….130°C/W
Thermal Resistance
θ
JA
……………….250°C/W
Junction Temperature(Note2)……….........160°C
Operating Temperature Range…….-40°C to 85°C
Lead Temperature(Soldering,10s)………...300°C
Storage Temperature Range……..-65°C to 150°C
ESD HBM(Human Body Mode)……………...2kV
ESD MM(Machine Mode)………………….200V
PACKAGE/ORDER INFORMATION
Order Part Number
TOP VIEW
SW
GND
FB
1
2
3
6
5
4
VIN
OV
EN
Package
SOT23-6
SOT23-6
SOT23-6
SOT23-6
Remark
V
FB
=104mV
V
FB
=104mV
V
FB
=250mV
V
FB
=300mV
Top Marking
B11G8W
B1A8DC
B1B8DC
B1C8DC
MT9284-28J
MT9284AS6
MT9284BS6
MT9284CS6
6-LEAD PLASTIC SOT-23
T
JMAX
= 160°C,
θ
JA
= 250°C/ W,
θ
JC
= 130°C/W
PIN DESCRIPTION
Pin Name
Pin Number
Description
Inductor Connection. Connect to the switched side of the external
inductor as well as the anode of the external diode. SW is high
impedance during shutdown.
Ground Pin.
Current-Sense Feedback Input. Connect a resistor from FB to GND to set
the LED current.
Enable and LED Brightness Control Input. Pull high to turn on IC.Drive EN
with a 20kHz to 1MHz unfiltered PWM dimming signal for DC LED
current that is proportional to the signal’s duty cycle.
Over Voltage Input.The MT9284 turn off the N-channel MOSFET when
V
OUT
exceeds 28V .Connect OV to the output at the top of the LED string.
Power Supply Input. Must be closely decoupled to GND with a 1µF or
greater ceramic capacitor.
SW
GND
FB
EN
OV
VIN
1
2
3
4
5
6
MT9284 Rev1.0
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AEROSEMI
MT9284 1.2MHz,High Efficiency Boost White LED Driver
ELECTRICAL CHARACTERISTICS
(Note 3)
(V
IN
=V
EN
=3.7V,T
A
= 25°C, unless otherwise noted.)
PARAMETER
CONDITIONS
Operating Input Voltage
Under Voltage Lockout
Under Voltage Lockout
Hysteresis
Current (Shutdown)
V
EN
<0.4V
V
FB
=0.15V，No switching
Quiescent Current
V
FB
=0V，switching
Supply Current
MT9284-28J
MT9284AS6
Regulated Feedback
Voltage
MT9284BS6
MT9284CS6
Switching Frequency
ON Resistance of NMOS
Peak Current Limit
V
IN
= 4.2V,Duty cycle=50%
EN Shutdown Voltage
EN Enable Voltage
EN Leakage Current
OVP Threshold
Open LED,V
OUT
Rising
MIN
2.5
TYP
2.2
100
0.1
200
0.6
104
104
250
300
1.2
0.5
1.5
1
300
1
114
114
262
315
MAX
5.5
2.45
UNIT
V
V
mV
µA
µA
mA
mV
mV
mV
mV
MHz
Ω
A
V
V
µA
V
94
94
238
285
0.4
1.5
±0.01
28
±1.0
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2: T
J
is calculated from the ambient temperature T
A
and power dissipation P
D
according to the
following formula: T
J
= T
A
+ (P
D
) x (250°C/W).
Note 3: 100% production test at 25°C. Specifications over the temperature range are guaranteed by design
and characterization.
MT9284 Rev1.0
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AEROSEMI
MT9284 1.2MHz,High Efficiency Boost White LED Driver
TYPICAL PERFORMANCE CHARACTERISTICS
20
LED Current vs. PWM Dimming @ 7S WLEDs
15
I
LED
(mA)
10
5
F=100kHz
7S1P WLEDs
0
0
20
40
60
80
100
PWM Duty Cycle(%)
MT9284 Rev1.0
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AEROSEMI
MT9284 1.2MHz,High Efficiency Boost White LED Driver
Normal Operation @ V
IN
=3V
Normal Operation @ V
IN
=3.7V
Normal Operation @ V
IN
=4.3V
Normal Operation @ V
IN
=5.5V
MT9284 Rev1.0
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Aerosemi Proprietary Information.Unauthorized Photocopy and Duplication Prohibited.
All Rights Reserved.
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